Crystal Structure of Carboxylase Reaction-oriented Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase from a Thermophilic Red Alga, Galdieria partita

Abstract

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) obtained from a thermophilic red alga Galdieria partita has the highest specificity factor of 238 among the Rubiscos hitherto reported. Crystal structure of activated Rubisco from G. partita complexed with the reaction intermediate analogue, 2-carboxyarabinitol 1,5-bisphosphate (2-CABP) has been determined at 2.4-Å resolution. Compared with other Rubiscos, different amino residues bring the structural differences in active site, which are marked around the binding sites of P-2 phosphate of 2-CABP. Especially, side chains of His-327 and Arg-295 show the significant differences from those of spinach Rubisco. Moreover, the side chains of Asn-123 and His-294 which are reported to bind the substrate, ribulose 1,5-bisphosphate, form hydrogen bonds characteristic of Galdieria Rubisco. Small subunits of Galdieria Rubisco have more than 30 extra amino acid residues on the C terminus, which make up a hairpin-loop structure to form many interactions with the neighboring small subunits. When the structures of Galdieria and spinach Rubiscos are superimposed, the hairpin region of the neighboring small subunit inGaldieria enzyme and apical portion of insertion residues 52–63 characteristic of small subunits in higher plant enzymes are almost overlapped to each other. Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) obtained from a thermophilic red alga Galdieria partita has the highest specificity factor of 238 among the Rubiscos hitherto reported. Crystal structure of activated Rubisco from G. partita complexed with the reaction intermediate analogue, 2-carboxyarabinitol 1,5-bisphosphate (2-CABP) has been determined at 2.4-Å resolution. Compared with other Rubiscos, different amino residues bring the structural differences in active site, which are marked around the binding sites of P-2 phosphate of 2-CABP. Especially, side chains of His-327 and Arg-295 show the significant differences from those of spinach Rubisco. Moreover, the side chains of Asn-123 and His-294 which are reported to bind the substrate, ribulose 1,5-bisphosphate, form hydrogen bonds characteristic of Galdieria Rubisco. Small subunits of Galdieria Rubisco have more than 30 extra amino acid residues on the C terminus, which make up a hairpin-loop structure to form many interactions with the neighboring small subunits. When the structures of Galdieria and spinach Rubiscos are superimposed, the hairpin region of the neighboring small subunit inGaldieria enzyme and apical portion of insertion residues 52–63 characteristic of small subunits in higher plant enzymes are almost overlapped to each other. Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco, EC4.1.1.39) 1The abbreviations used are: Rubisco, ribulose 1,5-bisphosphate carboxylase/oxygenase; RuBP, ribulose 1,5-bisphosphate; 3-PGA, 3-phosphoglycerate; L2, L1S1, L2S2, L4S4, L8S8, two large subunits, large and small subunits, two large and two small subunits, four large and four small subunits, holoenzyme of Rubisco; rbcS , small subunit gene of Rubisco; Sr, specificity factor; V C, maximum velocity of carboxylation; V O, maximum velocity of oxygenation; K O, Michaelis constant for O2; K C, Michaelis constant for CO2; k cat(C), maximum turnover numbers of carboxylation; k cat(O), maximum turnover numbers of oxygenation; 2-CABP, 2-carboxyarabinitol 1,5-bisphosphate is the rate-limiting enzyme in the Calvin-Benson cycle of photosynthesis. It catalyzes the addition of gaseous CO2 to ribulose 1,5-bisphosphate (RuBP) and produces two molecules of 3-phosphoglycerate (3-PGA) (1Andrews T.J. Lorimer G.H. Hatch M.D. Boardman N.K. The Biochemistry of Plants. 10. Academic Press, New York1987: 131-218Google Scholar, 2Cleland W.W. Andrews T.J. Gutteridge S. Hartman F.C. Lorimer G.H. Chem. Rev. 1998; 98: 549-561Crossref PubMed Scopus (344) Google Scholar). However, this enzyme also catalyzes O2 addition to RuBP as the primary reaction of photorespiration. The latter reaction yields one molecule each of 3-PGA and 2-phosphoglycolate from one molecule of RuBP. The oxygenation reaction reduces the photosynthetic efficiency up to 60% (3Zelitch I. Science. 1975; 188: 626-633Crossref PubMed Scopus (102) Google Scholar). Thus the improvement of the carboxylation/oxygenation ratio by genetic engineering has been attempted to increase the productivity of crop plants. For the activation of Rubisco, the reaction of CO2 with ε-amino group of conserved Lys-201 must occur to form carbamate, which is stabilized by Mg2+ (4Lorimer G.H. Biochemistry. 1981; 20: 1236-1240Crossref PubMed Scopus (98) Google Scholar). Carbamylation is necessary for both carboxylation and oxygenation reactions. Rubisco can be easily activated by including Mg2+ and bicarbonate in vitro, but in vivo activation requires a soluble chloroplast protein, Rubisco activase, and ATP (5Portis Jr., A.R. Biochim. Biophys. Acta. 1990; 1015: 15-28Crossref PubMed Scopus (108) Google Scholar). Rubisco exists as a hexadecamer (L8S8) composed of eight large and eight small subunits and its molecular mass is about 550,000 Da in all eukaryotes except dinoflagellates and many bacteria (1Andrews T.J. Lorimer G.H. Hatch M.D. Boardman N.K. The Biochemistry of Plants. 10. Academic Press, New York1987: 131-218Google Scholar). Another type of Rubisco is composed of only large subunits as found in some dinoflagellates and some photosynthetic bacteria,Rhodospirillum rubrum. The primary structure of Rubisco's large subunits of non-green algae lacking chlorophyll b are highly homologous to that of the β-purple bacterial enzyme, however, less homologous to those of the enzymes of higher plants, green algae, and cyanobacteria (6Morden C.W. Golden S.S. J. Mol. Evol. 1991; 32: 379-395Crossref PubMed Scopus (57) Google Scholar). In contrast, amino acid sequences of small subunits are less similar than those of large subunits across the Rubiscos. Small subunits of Rubisco genes (rbcS) are nuclear-encoded in green algae,Euglena and higher plants (1Andrews T.J. Lorimer G.H. Hatch M.D. Boardman N.K. The Biochemistry of Plants. 10. Academic Press, New York1987: 131-218Google Scholar, 7Tabita F.R. Microbiol. Rev. 1988; 52: 155-189Crossref PubMed Google Scholar). The small subunits of these Rubiscos have 12–18 amino acid insertions, which are not present in the plastid-encoded small subunits of non-green algae and β-purple bacteria. On the other hand, more than 30 extra amino acid residues exist on the C terminus in these organisms (8Assali N.-E. Martin W.F. Sommerville C.C. Loiseaux-de Goër S. Plant Mol. Biol. 1991; 17: 853-863Crossref PubMed Scopus (41) Google Scholar). From phylogenetic analysis, Rubisco genes are divided into three groups, α-purple bacterial, β-purple bacterial, and non-green algal, and γ-bacterial, cyanobacterial and plant groups (9Assali N.-E. Mache R. Loiseaux-de Goër S. Plant Mol. Biol. 1990; 15: 307-315Crossref PubMed Scopus (57) Google Scholar). Even though the structural difference among these groups is presumed, no crystal structure of the non-green algal group has been determined. The gaseous substrates CO2 and O2 are the competitive inhibitors of oxygenase and carboxylase, respectively. The carboxylation/oxygenation ratio is defined as CO2/O2 relative specificity factor (Sr),V c K o/V o K c, where V c and V o are maximum velocities of carboxylation and oxygenation, and K oand K c are the Michaelis constants for O2 and CO2, respectively (10Liang W.A. Ogren W.L. Hageman R.H. Plant Physiol. 1974; 54: 678-685Crossref PubMed Google Scholar). A high Sr value means the Rubisco with an effective carbon fixation activity. Rubisco from R. rubrum with L2 composition has the low Sr value of 15. In the case of Rubiscos with L8S8 composition, Sr values are 45 forSynechococcus, 70 for Chlamydomonas, and 93 for spinach (11Uemura K. Suzuki Y. Shinkai T. Wadano A. Jensen R.G. Chmara W. Yokota A. Plant Cell Physiol. 1996; 37: 325-331Crossref Scopus (50) Google Scholar). Moreover, Rubiscos from marine algae have been found to exhibit high Sr values over F.R. Biophys. PubMed Scopus Google Scholar). Especially, Rubiscos from thermophilic red algae show high Sr Rubisco partita has the Sr value of which is the highest among the Rubiscos hitherto reported K. S. Yokota A. Biophys. PubMed Scopus Google Scholar). C values are Galdieria and spinach and k are maximum turnover numbers of carboxylation and oxygenation, respectively. k are and in Galdieria and spinach Rubiscos, respectively. is only difference in carboxylation reaction these Rubiscos. On the other values are and for these Rubiscos, respectively. difference these Rubiscos is in the oxygenation The structure of Galdieria enzyme the of the for the oxygenation reaction K. S. Yokota A. Biophys. PubMed Scopus Google Scholar). Crystal structures of the of activated Rubiscos from and with 2-carboxyarabinitol 1,5-bisphosphate (2-CABP) have been reported T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, S. I. PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar, T. G. J. Biol. Chem. PubMed Google Scholar). to the active of Rubisco and an for the carboxylation and oxygenation of RuBP J. R. Biochemistry. PubMed Scopus Google Scholar). the crystal structure of Rubisco partita be and with those of other be to the structural to its high Sr the crystal structure of the of activated Rubisco from a thermophilic red alga G. at 2.4-Å resolution. is the on the crystal structure of Rubisco from β-purple bacterial and non-green algal Galdieria Rubisco with the as K. S. Yokota A. Biophys. PubMed Scopus Google Scholar). of Galdieria Rubisco has been reported T. K. Yokota A. Y. J. 1996; PubMed Scopus Google Scholar). However, a crystal form of obtained the improvement of The of crystal is higher than that of the reported the A. and of New Scholar). The of of of and 2-CABP, and of over a the crystal and of form and for the of of the form the obtained at K and for to a of in on of the the A. 1991; Scopus Google Scholar). and by the of S. of Scholar). The group of Rubisco determined to be with of a b of Rubisco in the the J. Mol. Biol. PubMed Scopus Google is to be to a of which is the value for by and S. of Scholar). A of from and for the and with the of Crystal structure of Galdieria Rubisco by the molecular The both large and small subunits of the activated Rubisco from complexed with J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). residues of the by by J. A. Scopus Google from the PubMed Scopus Google Scholar). A of in the is by the From the of found with high has two which are to a the structure is up to From the of and four have been The by the of with and J. Science. PubMed Scopus Google Scholar). The is in with one of the of the PubMed Scopus Google Scholar). the of one of of and When the of and and value the molecules by the difference at and at the the of The of the from and of with the J. Google Scholar). The that of the residues in the in the and in the of small The for all the and 2.4-Å and respectively. The from of the and and respectively. The is about as from the Google Scholar). Compared with spinach Rubisco, the large subunits of Galdieria Rubisco have and amino acid residues on and C respectively. In the Rubisco, the large subunits are in the for residues the small subunits are for all In the crystal structures of activated spinach and Rubiscos complexed with 2-CABP, the of the large subunits for residues I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). Galdieria Rubisco has a composed of by which is in cyanobacterial and plant Rubiscos. structures of Galdieria Rubisco are almost the except the extra in residues and the of in residues of the large subunits and spinach Rubiscos are both about 60% in the large subunits and both about in the small subunits, however, the differences in structures are these Rubiscos. The in structures spinach Rubiscos are for that spinach and Rubiscos is The in the large and the small subunits and spinach Rubiscos are and which a structural difference the small subunits than that the large of the Rubiscos and structure of Galdieria Rubisco sequences have been the crystal structure of activated spinach and Rubiscos complexed with T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). residues for binding are The residues which the structural around the active in Galdieria Rubisco with residues of the large subunit in Galdieria Rubisco are and different from the structure of spinach large subunit sequences of residues not The spinach has been used in Galdieria and other Rubiscos. structure in Galdieria Rubisco determined by the W. PubMed Scopus Google Scholar). structure is from S. I. J. Mol. Biol. 1990; PubMed Scopus Google Scholar). of the large subunit is only in Galdieria Rubisco. the PubMed Scopus Google in large subunit is and the large subunits composed of a L2 in higher plant and Rubiscos T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, S. I. PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). However, the is in Galdieria Rubisco. Moreover, Rubisco bonds of and S. I. PubMed Scopus Google Scholar, J. Biol. Chem. PubMed Google residues and are not in Galdieria Rubisco has no acid residues with are conserved and In Galdieria Rubisco, the is by the in the as in other Rubiscos of side chains of and and groups, and of T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, S. I. PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar, T. G. J. Biol. Chem. PubMed Google Scholar). are differences of and the structure of Galdieria and other Rubiscos. The binding of in Galdieria and other Rubiscos are almost the of the large subunits of residues and exists and in are conserved except small Rubiscos. Crystal structure of Rubisco an in J. Biol. Chem. PubMed Google Scholar). The of activated spinach Rubisco is In contrast, structures of activated Rubiscos complexed with a and the ε-amino group of to the group of and the side of T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, S. I. PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). the is defined as the the The of is necessary to bind the RuBP and the reaction complexed with also has the significant difference is found in the structure of the of Galdieria and spinach Rubiscos. of the in are not high in these Rubiscos that the is in the The side of a hydrogen to the of in and Rubiscos T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, S. I. PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). of β-purple bacterial and non-green algal Rubiscos is group with the make hydrogen bonds to the side of in Galdieria Rubisco However, the side of which to group of is different Galdieria and spinach Rubiscos. the is a the of the Rubisco holoenzyme The extra amino acid residues on the of the small subunit in Galdieria Rubisco make up hairpin-loop structure the of Galdieria Rubisco is than spinach Rubisco. The region of the small subunit many interactions with other with the neighboring small subunits. When the structures of Galdieria and spinach Rubiscos are superimposed, the hairpin region of the neighboring small subunit in Galdieria enzyme and apical portion of extra insertion residues 52–63 in spinach enzyme are almost overlapped to each other However, the insertion residues in spinach Rubisco only two hydrogen bonds to the large subunit composed of and no with neighboring small subunit T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar). The region in one hydrogen and one to the large subunit composed of Moreover, this region two hydrogen bonds to the neighboring large subunit around the In Galdieria Rubisco, of the small subunits the region in the of the small subunit and the group and the of make hydrogen bonds to the of and of the neighboring large respectively. bonds the two of of small subunit is almost conserved in β-purple bacterial and non-green algal group (8Assali N.-E. Martin W.F. Sommerville C.C. Loiseaux-de Goër S. Plant Mol. Biol. 1991; 17: 853-863Crossref PubMed Scopus (41) Google Scholar). The side of two Moreover, this region in the Compared with the active structures of spinach Rubiscos T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google J. Gutteridge S. J. Biol. Chem. PubMed Google Galdieria Rubisco has the structure around P-2 phosphate of 2-CABP. Especially, side chains of His-327 and Arg-295 show the significant structural differences from those of spinach Rubisco and the of in Galdieria Rubisco a hydrogen to the of In higher plants and is of the extra hydrogen in the of the side of of His-327 of R. rubrum Rubisco by and increase more than for RuBP with that of enzyme Hartman F.C. J. Biol. Chem. 1991; PubMed Google Scholar). His-327 to the K for RuBP. is conserved except Rubiscos from non-green algae, in which is In Galdieria Rubisco, the side of a hydrogen to the of is in the Rubiscos except β-purple bacterial and non-green algal of spinach Rubisco to The side of in Galdieria Rubisco, also a hydrogen to two different of interactions the structural difference around and on Arg-295 of Rubisco obtained from are almost of the carboxylation and are by 2-CABP. that Arg-295 is for the binding of the RuBP J. Biol. Chem. 1990; PubMed Google Scholar). Arg-295 also to for RuBP. Rubisco from the red has the value of F.R. Biophys. PubMed Scopus Google which is of the K of spinach Rubisco has a high with enzyme in both large and small K. K. PubMed Scopus Google and is to have a similar K to that of the the side structures of Arg-295 and His-327 the K RuBP in Galdieria Rubisco though of Galdieria Rubisco has not been determined. and on of Rubisco from A. are almost of oxygenase Biochemistry. PubMed Scopus Google Scholar). the oxygenase activity. The side chains of His-327 and in Galdieria Rubisco have the and are to each other in with that in spinach Rubisco The side of His-327 in Galdieria Rubisco be one of the structural to the specificity factor by a conserved except Rubiscos in β-purple bacterial and non-green algal to with the activity. However, the rubrum Rubisco a high of the with a of S. R. Hartman F.C. J. Biol. Chem. PubMed Google Scholar). Crystal structure of activated R. rubrum Rubisco complexed with the RuBP that the P-2 phosphate of RuBP is from the side chains of Arg-295 and and of the of the side of Arg-295 to T. G. J. Biol. Chem. 1991; PubMed Google Scholar). that the rubrum Rubisco. which is except small Rubiscos, the side of Arg-295 binding to P-2 phosphate of T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, S. I. PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). The P-2 phosphate of RuBP interactions not only to the side of Arg-295 but also to that of as in the crystal structure of enzyme complexed with the RuBP, and of Mg2+ I. J. Mol. Biol. PubMed Scopus Google Scholar). Moreover, in the activated spinach Rubisco complexed with 3-PGA, the side of a hydrogen to of 3-PGA I. Biochemistry. PubMed Scopus Google Scholar). that the except the small Rubiscos. When the structures and the activated Rubiscos binding are superimposed, the side of in enzyme to form no hydrogen with the P-2 phosphate of RuBP. The amino on be to the difference Galdieria and other Rubiscos. Compared with other Rubiscos, the side of His-294 inGaldieria Rubisco also has the different the of His-294 in Galdieria Rubisco a hydrogen to the of of the of and hydrogen the side chains of His-294 and His-294 and Asn-123 are the residues to bind in the active of the enzyme, the these residues the Rubisco. The side chains of His-294 obtained from both spinach and Rubiscos make a hydrogen to the group of Rubisco, the is also In the structures for the carboxylation and oxygenation show structural differences J. J. Mol. Scopus Google Scholar). The of is and for the structures of the carboxylation and oxygenation of RuBP, that a structural around group the in the carboxylation and The structural of the side of His-294 the Sr value in In Galdieria Rubisco, the amino acid residues around Lys-201 make hydrogen bonds In higher plants, is group a hydrogen to the side of However, inGaldieria Rubisco, is which is in the hydrogen On the other hand, inGaldieria Rubisco is of which group a hydrogen to the of However, in higher plants, is has the ε-amino group a of and high F.C. S. J. Biol. Chem. PubMed Google Scholar). on in R. rubrum Rubisco not the that the ε-amino group of of RuBP F.C. S. R. J. Biol. Chem. PubMed Google Scholar). However, this ε-amino group is from of in the structures of activated Rubiscos complexed with T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, S. I. PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). In Galdieria Rubisco, the ε-amino group of is also from the of 2-CABP. that the group of catalyzes the reaction W.W. Andrews T.J. Gutteridge S. Hartman F.C. Lorimer G.H. Chem. Rev. 1998; 98: 549-561Crossref PubMed Scopus (344) Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar). The group on Lys-201 to the of I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar, I. J. Mol. Biol. PubMed Scopus Google Scholar). Moreover, is to the of the of 3-PGA I. Biochemistry. PubMed Scopus Google Scholar, Hartman F.C. Biochemistry. 1996; PubMed Scopus Google Scholar). as as is an for the The hydrogen and Lys-201 to the of the side chains of and Lys-201 the The in that the is a rate-limiting in reaction Biochemistry. PubMed Scopus Google Scholar). Moreover, the of the that addition is rate-limiting W. J. Biol. Chem. PubMed Google Scholar). the the velocity of On the other hand, the CO2 in the chloroplast of plants is S. J. Plant Physiol. 1991; which is of the K spinach Rubisco. G. partita the with low CO2 is to Rubisco to to the with low CO2 In the efficiency of the reaction in Galdieria Rubisco is higher than that in spinach enzyme K. S. Yokota A. Biophys. PubMed Scopus Google Scholar). It means Rubisco the high velocity of the reaction low CO2 the hydrogen and Lys-201 a for the efficiency in In Galdieria Rubisco, the of which a with the side of is about from the in spinach Rubisco the side of with the and of in spinach Rubisco and the with only inGaldieria enzyme The group of of activated spinach Rubisco is about in with that of activated spinach enzyme complexed with T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. Biol. 1996; PubMed Scopus Google Scholar). In Galdieria Rubisco, the of the both of The structural of inGaldieria Rubisco to be on the hydrogen the of and the side of the structures around and are different and spinach Rubiscos. to is in β-purple bacterial and non-green algal Rubiscos, the is conserved by in the enzymes in other Rubisco, the residues around can the the reactions. The of in R. rubrum Rubisco only of the Sr value Hartman F.C. J. Biol. Chem. PubMed Google Scholar). The side of with the ratio the carboxylation and oxygenation of RuBP. The structural difference around the increase of the Sr Rubisco, the extra residues in the small subunit to make the interactions more In the reported structure of a large of PubMed Scopus Google Scholar, R. K. PubMed Scopus Google Scholar, I. R. A. R. J. Mol. Biol. PubMed Scopus Google Scholar). is and the numbers of of the enzymes from and are and respectively T.J. A. R. R. PubMed Scopus Google Scholar). G. partita is thermophilic and the for is about 45 Rubisco to have high The of in Galdieria Rubisco is in The numbers in spinach Rubisco is T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar). in Galdieria Rubisco are than that in spinach Rubisco. to to the Rubisco. The of the small subunits have not been but a in the small subunit a of the the from the active of the large subunits F.R. Biochemistry. PubMed Scopus Google Scholar). Rubiscos which are different in the large and small subunits have been to the of the small subunits. The Rubisco, which of the large subunits from and the small subunits from marine value up to Rubisco. However, the Sr value up to of the value in Rubisco F.R. Biochemistry. PubMed Scopus Google Scholar). The small subunits of Rubisco also have more than 30 extra residues on C terminus, which to be for the increase of the Sr However, in this region is from the than is not this extra region to an increase of the Sr However, residues of this region with large subunits in an to of the large subunit composed of residues are conserved in Rubiscos from the β-purple bacteria and non-green algae, form the However, of the large subunits in other Rubiscos with the small subunits T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar, I. J. Mol. Biol. 1996; PubMed Scopus Google Scholar, S. I. PubMed Scopus Google Scholar, J. Gutteridge S. J. Biol. Chem. PubMed Google Scholar). On the other hand, the of of the small subunits a hydrogen with inGaldieria Rubisco, which also to be in with Rubisco of the β-purple bacterial and non-green algal The and show that spinach Rubisco has two of small subunits. of the small subunits is T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google and is in the in the the L2 a hydrogen to the of of the neighboring large an to that of the In Galdieria Rubisco, the ε-amino group of a hydrogen to the of of the large subunits composed of and residues of small subunits residues and of the large subunits of the interactions in the spinach enzyme Rubisco has region of small subunits characteristic of non-green algal enzyme residues 52–63 of small subunits in higher plant The of these residues no the residues and It that the hydrogen of small subunits and of large subunits with the in the L2 of the higher plant enzymes T. K. Y. R. S. K. K. Yokota A. Y. J. Biol. Chem. 1996; PubMed Scopus Google Scholar). The small subunits of Galdieria Rubisco also make a hydrogen to of large Rubisco has the low Sr the hydrogen of large subunits and small subunit be with the increase of the Sr value inGaldieria to of and and of the for for in at the The structure on at the for are also to G. for the of this are also to the of the at the of