Thioredoxin-dependent Enzymatic Activation of Mercaptopyruvate Sulfurtransferase

Abstract

Rat 3-mercaptopyruvate sulfurtransferase (MST) contains three exposed cysteines as follows: a catalytic site cysteine, Cys247, in the active site and Cys154 and Cys263 on the surface of MST. The corresponding cysteine to Cys263 is conserved in mammalian MSTs, and Cys154 is a unique cysteine. MST has monomer-dimer equilibrium with the assistance of oxidants and reductants. The monomer to dimer ratio is maintained at ∼92:8 in 0.2 m potassium phosphate buffer containing no reductants under air-saturated conditions; the dimer might be symmetrical via an intersubunit disulfide bond between Cys154 and Cys154 and between Cys263 and Cys263, or asymmetrical via an intersubunit disulfide bond between Cys154 and Cys263. Escherichia coli reduced thioredoxin (Trx) cleaved the intersubunit disulfide bond to activate MST to 2.3- and 4.9-fold the levels of activation of dithiothreitol (DTT)-treated and DTT-untreated MST, respectively. Rat Trx also activated MST. On the other hand, reduced glutathione did not affect MST activity. E. coli C35S Trx, in which Cys35 was replaced with Ser, formed some adducts with MST and activated MST after treatment with DTT. Thus, Cys32 of E. coli Trx reacted with the redox-active cysteines, Cys154 and Cys263, by forming an intersubunit disulfide bond and a sulfenyl Cys247. A consecutively formed disulfide bond between Trx and MST must be cleaved for the activation. E. coli C32S Trx, however, did not activate MST. Reduced Trx turns on a redox switch for the enzymatic activation of MST, which contributes to the maintenance of cellular redox homeostasis. Rat 3-mercaptopyruvate sulfurtransferase (MST) contains three exposed cysteines as follows: a catalytic site cysteine, Cys247, in the active site and Cys154 and Cys263 on the surface of MST. The corresponding cysteine to Cys263 is conserved in mammalian MSTs, and Cys154 is a unique cysteine. MST has monomer-dimer equilibrium with the assistance of oxidants and reductants. The monomer to dimer ratio is maintained at ∼92:8 in 0.2 m potassium phosphate buffer containing no reductants under air-saturated conditions; the dimer might be symmetrical via an intersubunit disulfide bond between Cys154 and Cys154 and between Cys263 and Cys263, or asymmetrical via an intersubunit disulfide bond between Cys154 and Cys263. Escherichia coli reduced thioredoxin (Trx) cleaved the intersubunit disulfide bond to activate MST to 2.3- and 4.9-fold the levels of activation of dithiothreitol (DTT)-treated and DTT-untreated MST, respectively. Rat Trx also activated MST. On the other hand, reduced glutathione did not affect MST activity. E. coli C35S Trx, in which Cys35 was replaced with Ser, formed some adducts with MST and activated MST after treatment with DTT. Thus, Cys32 of E. coli Trx reacted with the redox-active cysteines, Cys154 and Cys263, by forming an intersubunit disulfide bond and a sulfenyl Cys247. A consecutively formed disulfide bond between Trx and MST must be cleaved for the activation. E. coli C32S Trx, however, did not activate MST. Reduced Trx turns on a redox switch for the enzymatic activation of MST, which contributes to the maintenance of cellular redox homeostasis. Redox-active disulfide bonds have an important role in regulating protein function and enzymatic activity. Reduced thioredoxin (Trx) 2The abbreviations used are: Trx, thioredoxin; DTT, dithiothreitol; MST, mercaptopyruvate sulfurtransferase; TRD, thioredoxin reductase; HPLC, high pressure liquid chromatography. cleaves the disulfide bond, “turns on or off a redox switch,” and facilitates protein function or activates an enzyme that results from possible conformational changes (1Clancey C.J. Gilbert H.F. J. Biol. Chem. 1987; 262: 13545-13549Abstract Full Text PDF PubMed Google Scholar, 2Hawkins H.C. Blackburn E.C. Freedman R.B. Biochem. J. 1991; 275: 349-353Crossref PubMed Scopus (96) Google Scholar, 3Sasaki Y. Kozaki A. Hatano M. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 11096-11101Crossref PubMed Scopus (134) Google Scholar, 4Mora-Garcia S. Rodriguez-Suarez R. Wolosiuk R.A. J. Biol. Chem. 1998; 273: 16273-16280Abstract Full Text Full Text PDF PubMed Scopus (46) Google Scholar, 5Zheng M. Aslund F. Storz G. Science. 1998; 279: 1718-1721Crossref PubMed Scopus (979) Google Scholar, 6Reynolds C.M. Poole L.B. Biochemistry. 2001; 40: 3912-3919Crossref PubMed Scopus (24) Google Scholar, 7Buhrman G. Parker B. Sohn J. Rudolph J. Mattos C. Biochemistry. 2005; 44: 5307-5316Crossref PubMed Scopus (91) Google Scholar, 8Sevier C.S. Kaiser C.A. Mol. Biol. Cell. 2006; 17: 2256-2266Crossref PubMed Scopus (60) Google Scholar). These disulfide bonds are generally “intrasubunit or intramolecular disulfide bonds.” When these cysteines are adjacent, the redox change most effectively turns the redox switch on and off (9Park C. Raines R.T. Protein Eng. 2001; 14: 939-942Crossref PubMed Scopus (44) Google Scholar). As an exceptional case, hetero-oligomer ATP synthase is inhibited via the formation of an intersubunit disulfide bond between the bc′ and γ subunits because of a mechanical standstill of the molecular motor (10Suzuki T. Suzuki J. Mitome N. Ueno H. Yoshida M. J. Biol. Chem. 2000; 275: 37902-37906Abstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar). This redox switch directly regulates enzymatic activity and can therefore be categorized as a direct and mechanical function. In the cases in which protein function is facilitated via a conformational change caused by cleavage of a disulfide bond, the redox switch is categorized as an indirect function. Rat 3-mercaptopyruvate sulfurtransferase (MST) (EC 2.8.1.2) is a 32.8-kDa simple protein enzyme (11Nagahara N. Nishino T. J. Biol. Chem. 1996; 271: 27395-27401Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar). MST catalyzes the degradation of cysteine, detoxifies cyanide (12Nagahara N. Ito T. Minami M. Histol. Histopathol. 1999; 14: 1277-1286PubMed Google Scholar), and serves as anti-oxidant protein (13Nagahara N. Katayama A. J. Biol. Chem. 2005; 280: 34569-34576Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar). When oxidative stress builds up in the cells, a sulfur atom of the catalytic site Cys247 donates an electron to the oxidants, and the cysteine is transiently converted to a sulfenate, resulting in the inhibition of MST. Furthermore, as the sulfenate is at a low redox potential, Trx and DTT reduce it to restore its activity, but reduced glutathione does not affect the activity (13Nagahara N. Katayama A. J. Biol. Chem. 2005; 280: 34569-34576Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar). Under oxidizing conditions, the cysteine pool is increased because of post-translational inhibition of methionine synthase (14Taoka S. Ohja S. Shan X. Kruger W.D. Banerjee R. J. Biol. Chem. 1998; 273: 25179-25184Abstract Full Text Full Text PDF PubMed Scopus (225) Google Scholar, 15Mosharov E. Cranford M.R. Banerjee R. Biochemistry. 2000; 39: 13005-13011Crossref PubMed Scopus (437) Google Scholar) and post-translational activation of cystathione β-synthase (14Taoka S. Ohja S. Shan X. Kruger W.D. Banerjee R. J. Biol. Chem. 1998; 273: 25179-25184Abstract Full Text Full Text PDF PubMed Scopus (225) Google Scholar, 16Chen Z. Chakraborty S. Shan X. Kruger W.D. Banerjee R. J. Biol. Chem. 1995; 270: 19246-19249Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar). Inhibition of MST conserves cysteine and contributes to increase the cysteine pool. An increase in the cysteine content in the cell results in an increase in the content of cellular reductants such as Trx and glutathione. Thus, MST contributes to maintain redox homeostasis. In a preliminary study, Escherichia coli reduced Trx activated rat recombinant MST after treatment with DTT, but DTT did not activate MST after treatment with reduced Trx. These findings suggested that reduced Trx reacted with cysteines other than Cys247. It is also possible that Trx reacted with Cys154 and Cys263 on the surface of MST. MST monomer-dimer equilibrium N. N. Chem. 2006; PubMed Scopus Google Scholar). The of rat MST N. T. Nishino T. J. Biol. Chem. 1995; 270: Full Text Full Text PDF PubMed Scopus Google Scholar) on the of G. J. 273: PubMed Scopus Google Scholar), that Cys154 and Cys263 in the are from other to an disulfide The dimer is therefore formed via intersubunit disulfide and reduced Trx with the disulfide bond or on redox Rat Trx has redox-active cysteine and and cysteine and Y. R.T. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), which are to of Trx A. F. F. J. Biol. Chem. Full Text PDF PubMed Google Scholar). is to an disulfide bond G. 2001; PubMed Scopus Google Scholar) and to S. M. E. T. M. G. A. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). Furthermore, the Trx with a which a of change in the protein function On the other hand, exposed cysteines are redox-active cysteines and in E. coli Trx R. R. M. B. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar). Thus, E. coli Trx has used to a of mammalian protein function A. J. Biol. Chem. Full Text PDF PubMed Google Scholar, Biochem. PubMed Scopus Google Scholar, J. A. J. Biol. Chem. Full Text PDF PubMed Google Scholar). In study, that E. coli thioredoxin on rat MST. The results that reduced Trx also regulates MST at the enzyme via a redox of intersubunit disulfide Rat which is replaced with and MST to a (13Nagahara N. Katayama A. J. Biol. Chem. 2005; 280: 34569-34576Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar). A a MST, which Cys154 and Cys263 are replaced with was A MST a between the was used as a for the The and used to of Cys263 with The was a The for the as follows: for the of at for for the of at for at for and at for The was with and for in at for was to the to the of Cys263 with The was by containing of the or MST was E. with a containing and enzyme was and to the (11Nagahara N. Nishino T. J. Biol. Chem. 1996; 271: 27395-27401Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar). E. coli thioredoxin and C35S Trx rat and Trx to the of T. S. H. Y. and T. for These and T. S. H. Y. and T. for Rat was from The with DTT on for in of potassium phosphate with a and with a Rat redox Trx be to a dimer via an disulfide bond, after DTT is Thus, the rat Trx, in which redox-active cysteines are is as a rat reduced Trx. In the after of MST with and E. coli or rat Trx and and E. coli or rat and in of potassium phosphate on for a of the was used for the activity In the E. coli or rat reduced Trx after of MST with E. coli or rat reduced Trx and in of potassium phosphate on for a of the was used for the activity the rat reduced Trx with DTT was also activation of MST in the E. coli or rat reduced Trx or the coli coli or was in of potassium phosphate on for and and the was used for the activity Furthermore, the rat reduced Trx with DTT and the with DTT also an sulfur of some MST, MST was with a of potassium cyanide in potassium phosphate on for and cyanide was a and with a molecular In an activation DTT, or E. coli or rat reduced Trx, after of MST with a of DTT or a of reduced Trx in potassium phosphate on for DTT was a and and with a When MST was activated in the MST was in a coli coli or in potassium phosphate on for or MST activity was and the ratio of the activity of to was the of MST activation by reduced Trx, of and activated and by reduced Trx As the of potassium cyanide not with N. T. Nishino T. J. Biol. Chem. 1995; 270: Full Text Full Text PDF PubMed Scopus Google Scholar), and for with a of potassium cyanide at of of with or reduced Trx in of potassium phosphate on for activity was an containing potassium cyanide and or the of MST, after of MST was with or reduced Trx or DTT, activity was an containing potassium and or of the under conditions, in the was a by and with was by a of a of and with DTT in of potassium phosphate on under conditions, DTT was from with a enzyme was with in potassium phosphate at for and the change in at was The ratio of of enzyme under air-saturated to that under was Trx of and with E. coli reduced E. coli or E. coli C35S Trx in of potassium phosphate on for and C35S MST with DTT in of potassium phosphate on for and an and with and which in The was of 0.2 m potassium phosphate the was and was at the a containing and was Trx MST was with E. coli reduced C32S Trx or or reduced C35S Trx or in of potassium phosphate on for a of the was for the activity. was with DTT on for and for activity. A to activity by the from mercaptopyruvate to not be for because disulfide bonds formed between subunits in the MST activity, which catalyzes from to cyanide (11Nagahara N. Nishino T. J. Biol. Chem. 1996; 271: 27395-27401Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar, N. T. Nishino T. J. Biol. Chem. 1995; 270: Full Text Full Text PDF PubMed Scopus Google it was activity of MST that was The protein with a protein with as the and of of MST by Reduced Trx and was activated in a by the E. coli or rat reduced Trx and also by the E. coli or rat reduced MST activation with of in These findings to rat Trx, E. coli Trx with rat MST. In the E. coli MST activity increased to that of the with E. coli Trx and E. coli and In the rat MST activity increased to that of the with rat Trx and rat and In the E. coli reduced Trx MST activity increased to that of the with E. coli Trx In the rat reduced Trx MST activity increased to that of the with rat Trx It is that treatment with DTT increased MST activity to that of the that DTT on rat Trx to its function directly activated MST the in study, that the ratio of to coli reduced coli and was to and and the ratio of to reduced and was to and respectively. the reduced Trx that the ratio of to was to MST by DTT, Reduced Trx, and coli reduced Trx, the E. coli and DTT activated and under air-saturated The of E. coli reduced Trx on the activation of MST was to that of the E. coli and to the and for MST and low to the and increased to and that of activation by the reduced Trx and activity of a in which MST was with E. coli Trx with and activity of an activity of a in which MST was with E. coli reduced activity of a in which DTT was on a after treatment of MST with activity of a in which DTT was on a after treatment of MST with DTT, and the MST was by E. coli reduced activity of a in which DTT was after MST was by E. coli reduced Trx. MST be from the of MST and rat Trx and rat are as a ratio of activity to that of or reduced MST. is of the not rat Trx and rat are as a ratio of activity to that of or reduced MST. is of the not rat Trx and rat are as a ratio of activity to that of or reduced MST. is of the not rat Trx and rat are as a ratio of activity to that of or reduced MST. is of the not rat Trx and rat are as a ratio of activity to that of or reduced MST. is of the not activity of a in which MST was with E. coli Trx with and activity of an activity of a in which MST was with E. coli reduced activity of a in which DTT was on a after treatment of MST with activity of a in which DTT was on a after treatment of MST with DTT, and the MST was by E. coli reduced activity of a in which DTT was after MST was by E. coli reduced Trx. MST be from the of MST and The rat Trx and rat are as a ratio of activity to that of or reduced MST. is of the not in a DTT also activated to between and the activity of Furthermore, that reduced Trx MST, in which oxidants formed a sulfenate at a catalytic Cys247, and DTT or the activity (13Nagahara N. Katayama A. J. Biol. Chem. 2005; 280: 34569-34576Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar). This and the results of that Cys154 and Cys263, other than the catalytic Cys247, are of for Trx and DTT, and DTT on a sulfenyl Cys247. the of Trx on a sulfenyl Cys247, after the with DTT and the DTT was with E. coli reduced Trx. and activated to that of MSTs, respectively. On the other hand, after with E. coli reduced Trx, with DTT. between and that of MST. The results that E. coli reduced Trx on Cys154 and Cys263 other than Cys247 in the activation of MST. The results of a rat Trx and rat are in and The rat and rat reduced Trx activated MST to and that of the respectively. It is DTT in the rat Trx, these increased to and that of the and These findings are to of E. coli Trx and E. coli It is suggested that DTT rat Trx function to activate MST because of of an intersubunit disulfide bond at in a rat Trx which The rat Trx is not for a of Trx function on a of the the of E. coli Trx on Cys263, and Cys247 of be the results of the activation and for and are in and In MST, for that the activation Furthermore, of the did not at a that the activation with of reduced Trx an increase in and a in The activation via of the of a enzyme with also under of Trx to and from possible conformational in for activity of MST in enzymatic is in which MST was by E. coli reduced Trx is for as a used a of at is for of for for activity to that for for is for as a used a of at is for of for for activity to that for for is of for MST to for An is for as a used a of at is for of for for activity to that for for is A in which MST was by E. coli reduced Trx is of for MST to for MST. in a for and a and the of for and On the other hand, for and These three low to reduced Trx, and the for and Furthermore, the of for MST with that for the MST and respectively. These findings that and the active of MST. The and for MST and respectively. E. coli of and that monomer of and the dimer and respectively. It is that MST of a monomer E. coli reduced Trx the dimer content to not and not at enzyme was activated DTT the dimer content of MST to at and to at These that an intersubunit disulfide bond can be formed between Cys154 of and of the other Cys263 and or Cys154 and a disulfide bond between Cys263 and in MST is that between Cys154 and in MST is formed but is to be reduced than in MST. Thus, an intersubunit disulfide bond be formed between Cys154 and Cys263 under of Trx to coli reduced C32S Trx with or DTT treatment did not activate MST On the other hand, E. coli reduced C35S Trx with or DTT treatment activated MST to and that of the that E. coli reduced C32S Trx did not change the dimer content under air-saturated On the other hand, E. coli reduced C35S Trx dimer and monomer and the was with the that an Trx an Trx an Trx a Trx a Trx and a Trx formed be in Furthermore, DTT treatment the of these These findings that Cys32 of Trx an intersubunit disulfide bond and a sulfenyl Cys247 to of of coli C35S Trx A symmetrical or asymmetrical dimer of MST with E. coli C35S Trx to of Trx which are in the after treatment of MST with reduced C35S Trx When Cys247 of MST is C35S Trx and Trx is formed via a disulfide bond formation between Cys247 of MST and Cys32 of C35S Trx. This is not in but the of the Trx is When Trx with an intersubunit disulfide of MST, a disulfide bond between Cys32 of C35S Trx and Cys154 or of MST is resulting in formation of monomer monomer is by to is Furthermore, C35S Trx These C35S Trx is and the in of of the Trx on the in of C35S Trx to that of MST not a dimer a monomer MST. are in the A rat reduced Trx, in which to Cys35 of E. coli Trx, was Reduced Trx with or DTT treatment activated MST to and that of the respectively. Rat recombinant MST a monomer-dimer equilibrium with assistance of cellular redox and the monomer to dimer ratio was to in 0.2 m potassium phosphate On the other hand, rat MST from the also a monomer-dimer with a ratio of to N. N. Chem. 2006; PubMed Scopus Google Scholar). oxidants other than in the might increase the dimer the ratio of intersubunit disulfide Trx effectively reduced the bonds to activate MST. The monomer-dimer equilibrium increase the dimer formed a sulfenate at Cys247 to MST, and DTT and Trx reduced MST to restore the activity, but glutathione did not affect the MST activity (13Nagahara N. Katayama A. J. Biol. Chem. 2005; 280: 34569-34576Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar). Under air-saturated conditions, after some containing sulfenyl Cys247 with reduced Trx, DTT did to activate MST. On the other hand, after MST with DTT Trx was activated by MST via of the intersubunit disulfide It has that disulfide serves as a redox switch for the of protein function (1Clancey C.J. Gilbert H.F. J. Biol. Chem. 1987; 262: 13545-13549Abstract Full Text PDF PubMed Google Scholar, 2Hawkins H.C. Blackburn E.C. Freedman R.B. Biochem. J. 1991; 275: 349-353Crossref PubMed Scopus (96) Google Scholar, 3Sasaki Y. Kozaki A. Hatano M. Proc. Natl. Acad. Sci. U. S. A. 1997; 94: 11096-11101Crossref PubMed Scopus (134) Google Scholar, 4Mora-Garcia S. Rodriguez-Suarez R. Wolosiuk R.A. J. Biol. Chem. 1998; 273: 16273-16280Abstract Full Text Full Text PDF PubMed Scopus (46) Google Scholar, 5Zheng M. Aslund F. Storz G. Science. 1998; 279: 1718-1721Crossref PubMed Scopus (979) Google Scholar, 6Reynolds C.M. Poole L.B. Biochemistry. 2001; 40: 3912-3919Crossref PubMed Scopus (24) Google Scholar, 7Buhrman G. Parker B. Sohn J. Rudolph J. Mattos C. Biochemistry. 2005; 44: 5307-5316Crossref PubMed Scopus (91) Google Scholar, 8Sevier C.S. Kaiser C.A. Mol. Biol. Cell. 2006; 17: 2256-2266Crossref PubMed Scopus (60) Google Scholar, C. Raines R.T. Protein Eng. 2001; 14: 939-942Crossref PubMed Scopus (44) Google Scholar). The findings that intersubunit disulfide serves as a redox switch for enzyme activation is of under air-saturated of and of under air-saturated is of under reduced is are the of of MST than of and are under and The of under air-saturated is The of under reduced is are the of of MST than of and are under and in a the MST activity was increased by reduced Trx, was increased and was with an increase of reduced Trx This activation did not because the activation DTT also activated MST via of a sulfenyl Cys247 with an increase in and a in This activation also The of the intersubunit disulfide bond be because the of a sulfenyl Cys247 by reduced Trx or DTT but As DTT reduced the sulfenate at Cys247 and reduced the intersubunit disulfide bond, the activation of MST by reduced Trx can be as an via of the intersubunit disulfide Reduced Trx and DTT did not increase and MST activity, and of these to of MST, which was activated by reduced Trx. These findings that cleavage of the disulfide bonds the conformational change that is for MST to the activated and on for activity was via of catalytic site Cys247, and DTT and reduced Trx the activity. The results that and an active of MST. Cys32 of E. coli Trx with a redox-active cysteine of a protein A. J. Biol. Chem. Full Text PDF Google Scholar). In study, Cys32 of E. coli Trx and of rat Trx reacted with MST at Cys263, and sulfenyl Cys247 and of E. coli C35S adducts and rat adducts via a disulfide bond that might be in the redox with in of and and Furthermore, cleavage of the disulfide bond between E. coli C35S or rat was for the enzymatic activation. Thus, MST was activated via cleavage of the with Trx. E. coli C35S Trx with DTT also activated and not These findings also that monomer-dimer equilibrium in MST is by redox Cys154 of rat MST is a unique cysteine on the surface of the and the corresponding cysteine is in E. coli H. T. M. T. J. Biol. Chem. Scholar), J. A. J. Biochem. 2000; PubMed Scopus Google Scholar), and R.A. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar), C.M. B. H. T. J. F. M. S. C. S. S. X. R.A. J. E. M. A. S. A. M. A. Y. J. J. U. A. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar), and R. C. Biochem. 1991; Scopus Google Scholar) On the other hand, Cys263 is conserved and A symmetrical dimer via a disulfide bond between Cys154 and Cys154 is formed in MST, the disulfide bond between Cys263 and Cys263 is to in MST than a dimer of MST, because the redox of Cys263 is than that of Cys154 in with symmetrical via an intersubunit disulfide bond between Cys154 and Cys154 and between Cys263 and Cys263, and an asymmetrical dimer via an intersubunit disulfide bond between Cys154 and Cys263. A of reduced Trx and regulates the equilibrium in in These findings are with the that rat recombinant MST a in a Trx also regulates the activity of in a and most effectively the enzyme activity via of the disulfide bond and DTT R. A. A. Proc. Natl. Acad. Sci. U. S. A. 2005; PubMed Scopus Google Scholar). The of for enzyme is by a in the active MST does not an disulfide bond is for Trx G. J. J. Mol. Biol. PubMed Scopus Google Scholar, T. Y. A. G. Proc. Natl. Acad. Sci. U. S. A. 2001; PubMed Scopus Google Scholar), Cys154 and Cys263 of rat MST are or to of rat and E. coli In mammalian cells, Trx is F. N. Y. Y. T. S. H. H. J. 1995; PubMed Scopus Google Scholar, H. S. M. J. A. 1996; PubMed Scopus Google Scholar, N. Y. M. H. Y. H. J. J. PubMed Scopus Google Scholar). On the that cellular protein content is J. and Scholar, of B. Scholar), MST on to be N. T. Nishino T. J. Biol. Chem. 1995; 270: Full Text Full Text PDF PubMed Scopus Google Scholar, N. Ito T. H. Nishino T. Biol. 1998; PubMed Scopus Google Trx between and that of MST, and therefore Trx can activate MST. Furthermore, after of MST with E. coli or rat Trx, and E. coli or rat between and A. J. Biol. Chem. Full Text PDF Google Scholar, A. J. Biochem. PubMed Scopus Google Scholar, E. C.A. C. J. PubMed Scopus Google Scholar), the activity was activity increased to and that of respectively. The MST activation can the other in MST serves as an protein via the formation of a sulfenate at Cys247, and cellular redox regulates the enzymatic activity (13Nagahara N. Katayama A. J. Biol. Chem. 2005; 280: 34569-34576Abstract Full Text Full Text PDF PubMed Scopus (91) Google Scholar). the are from oxidizing conditions, reduced Trx turns on the redox switch Trx cleaves an intersubunit disulfide to activate MST that results from possible conformational The results of that MST in the maintenance of cellular redox homeostasis. Nishino of and and of for