Mitochondrial NADH-Ubiquinone Oxidoreductase (Complex I)

Abstract

It has been shown that treatment of bovine mitochondrial complex I (NADH-ubiquinone oxidoreductase) with NADH or NADPH, but not with NAD or NADP, increases the susceptibility of a number of subunits to tryptic degradation. This increased susceptibility involved subunits that contain electron carriers, such as FMN and iron-sulfur clusters, as well as subunits that lack electron carriers. Results shown elsewhere on changes in the cross-linking pattern of complex I subunits when the enzyme was pretreated with NADH or NADPH (Belogrudov, G., and Hatefi, Y. (1994)Biochemistry 33, 4571–4576) also indicated that complex I undergoes extensive conformation changes when reduced by substrate. Furthermore, we had previously shown that in submitochondrial particles the affinity of complex I for NAD increases by ≥20-fold in electron transfer from succinate to NAD when the particles are energized by ATP hydrolysis. Together, these results suggest that energy coupling in complex I may involve protein conformation changes as a key step.In addition, it has been shown here that treatment of complex I with trypsin in the presence of NADPH, but not NADH or NAD(P), produced from the 39-kDa subunit a 33-kDa degradation product that resisted further hydrolysis. Like the 39-kDa subunit, the 33-kDa product bound to a NADP-agarose affinity column, and could be eluted with a buffer containing NADPH. It is possible that together with the acyl carrier protein of complex I the NADP(H)-binding 39-kDa subunit is involved in intramitochondrial fatty acid synthesis. It has been shown that treatment of bovine mitochondrial complex I (NADH-ubiquinone oxidoreductase) with NADH or NADPH, but not with NAD or NADP, increases the susceptibility of a number of subunits to tryptic degradation. This increased susceptibility involved subunits that contain electron carriers, such as FMN and iron-sulfur clusters, as well as subunits that lack electron carriers. Results shown elsewhere on changes in the cross-linking pattern of complex I subunits when the enzyme was pretreated with NADH or NADPH (Belogrudov, G., and Hatefi, Y. (1994)Biochemistry 33, 4571–4576) also indicated that complex I undergoes extensive conformation changes when reduced by substrate. Furthermore, we had previously shown that in submitochondrial particles the affinity of complex I for NAD increases by ≥20-fold in electron transfer from succinate to NAD when the particles are energized by ATP hydrolysis. Together, these results suggest that energy coupling in complex I may involve protein conformation changes as a key step. In addition, it has been shown here that treatment of complex I with trypsin in the presence of NADPH, but not NADH or NAD(P), produced from the 39-kDa subunit a 33-kDa degradation product that resisted further hydrolysis. Like the 39-kDa subunit, the 33-kDa product bound to a NADP-agarose affinity column, and could be eluted with a buffer containing NADPH. It is possible that together with the acyl carrier protein of complex I the NADP(H)-binding 39-kDa subunit is involved in intramitochondrial fatty acid synthesis. Among the enzyme complexes of the mitochondrial electron transport/oxidative phosphorylation system, complex I (NADH-ubiquinone oxidoreductase) has the most complicated structure and mechanism of action. The enzyme is composed of ≥43 subunits (1Fearnley I.M. Walker J.E. Biochim. Biophys. Acta. 1992; 1140: 105-134Crossref PubMed Scopus (292) Google Scholar, 2Walker J.E. Q. Rev. Biophys. 1992; 25: 253-324Crossref PubMed Scopus (685) Google Scholar), and contains one FMN and 5 EPR-visible iron-sulfur clusters, designated centers N1a, N1b, N2, N3, and N4 (3Sled' V.D. Friedrich T. Leif H. Weiss H. Meinhardt S.W. Fukumori Y. Calhoun M.W. Gennis R.B. Ohnishi T. J. Bioenerg. Biomembr. 1993; 25: 347-356Crossref PubMed Scopus (85) Google Scholar). Chemical analysis of iron and sulfide suggested the possible presence of 8 iron-sulfur clusters per FMN (4Ragan C.I. Galante Y.M. Hatefi Y. Biochemistry. 1982; 21: 2518-2524Crossref PubMed Scopus (41) Google Scholar). These results agreed with more recent data on the amino acid sequences of complex I subunits, in which 8 cysteine motifs were found for ligating 6 tetranuclear and 2 binuclear iron-sulfur clusters (1Fearnley I.M. Walker J.E. Biochim. Biophys. Acta. 1992; 1140: 105-134Crossref PubMed Scopus (292) Google Scholar,2Walker J.E. Q. Rev. Biophys. 1992; 25: 253-324Crossref PubMed Scopus (685) Google Scholar). Early studies showed that bovine complex I could be resolved into three domains, designated as flavoprotein (FP), 1The abbreviations used are: FP, flavoprotein; IP, iron-sulfur protein; HP, hydrophobic protein; TPCK,N-tosyl-l-phenylalanine chloromethyl ketone; Q1, ubiquinone-1. iron-sulfur protein (IP), and hydrophobic protein (HP) (5Hatefi Y. Stempel K.E. Biochem. Biophys. Res. Commun. 1967; 26: 301-308Crossref PubMed Scopus (33) Google Scholar, 6Hatefi Y. Annu. Rev. Biochem. 1985; 54: 1015-1069Crossref PubMed Google Scholar). This tridomain architecture appears to be the structural design of complex I from Neurospora crassa mitochondria (≥35 subunits) (7Schulte U. Fecke W. Krüll C. Nehls U. Schmiede A. Schneider R. Ohnishi T. Weiss H. Biochim. Biophys. Acta. 1994; 1187: 121-124Crossref PubMed Scopus (46) Google Scholar), Escherichia coli plasma membrane (13 subunits) (8Friedrich T. Steinmüller K. Weiss H. FEBS Lett. 1995; 367: 107-111Crossref PubMed Scopus (245) Google Scholar, 9Blattner F.R. Plunkett III, G. Bloch C.A. Perna N.T. Burland V. Riley M. Collado-Vides J. Glasner J.D. Rode C.K. Mayhew G.F. Gregor J. Davis N.W. Kirkpatrick H.A. Goeden M.A. Rose D.J. Mau B. Shao Y. Science. 1997; 277: 1453-1462Crossref PubMed Scopus (6115) Google Scholar), and possiblyParacoccus denitrificans (14 subunits) (10Takano S. Yano T. Yagi T. Biochemistry. 1996; 35: 9120-9127Crossref PubMed Scopus (44) Google Scholar). Bovine FP is water-soluble; it is composed of three subunits with molecular masses of 51, 24, and 9 kDa, and it contains per mol 1 FMN, a tetranuclear iron-sulfur cluster, and a binuclear iron-sulfur cluster. Data from the bovine (11Deng P.S.K. Hatefi Y. Chen S. Biochemistry. 1990; 29: 1094-1098Crossref PubMed Scopus (40) Google Scholar), the Paracoccus (12Yano T. Sled' V.D. Ohnishi T. Yagi T. J. Biol. Chem. 1996; 271: 5907-5913Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar), and the E. coli(13Fecke W. Sled' V.D. Ohnishi T. Weiss H. Eur. J. Biochem. 1994; 220: 551-558Crossref PubMed Scopus (83) Google Scholar) enzymes have indicated that the 51-kDa subunit binds NAD(H) and contains FMN and a tetranuclear cluster (center N3), and the 24-kDa subunit contains a binuclear cluster (likely center N1a). The bovine IP is also water-soluble, and is composed of seven major polypeptides with molecular masses of 75, 49, 30, 18, 15, 13, and 11 kDa, of which the last two comigrate at Mr ∼13,000 upon SDS-polyacrylamide gel electrophoresis (14Hatefi Y. Ragan C.I. Galante Y.M. Martonosi A.N. The Enzymes of Biological Membranes. Plenum Press, New York1985: 1-70Google Scholar, 15Masui R. Wakabayashi S. Matsubara H. Hatefi Y. J. Biochem. (Tokyo). 1991; 109: 534-543Crossref PubMed Scopus (17) Google Scholar). Only the 75-kDa subunit houses iron-sulfur clusters, and data from the Paracoccus enzyme have shown that the bacterial analogue of this subunit contains a tetranuclear, a binuclear (likely center N1b), and possibly another tetranuclear iron-sulfur cluster (16Yano T. Yagi T. Sled' V.D. Ohnishi T. J. Biol. Chem. 1995; 270: 18264-18270Abstract Full Text Full Text PDF PubMed Scopus (56) Google Scholar). In addition, a 23-kDa subunit of complex I contains 2 cysteine motifs for housing tetranuclear clusters, and a 20-kDa subunit has a motif of 3 cysteine residues that could ligate another tetranuclear cluster (2Walker J.E. Q. Rev. Biophys. 1992; 25: 253-324Crossref PubMed Scopus (685) Google Scholar). Electron microscopic studies of membrane crystals of Neurospora complex I and its peripheral (FP + IP) and integral (HP) segments have indicated that complex I is L-shaped, with one arm of the L being extramembranous and composed of subunits corresponding to those of bovine FP and IP, and the other arm being within the membrane and containing the hydrophobic subunits of the enzyme (17Hofhaus G. Weiss H. Leonard K. J. Mol. Biol. 1991; 221: 1027-1043Crossref PubMed Scopus (169) Google Scholar). This hydrophobic domain (HP) contains in both the bovine and the Neurospora complex I the 7 mitochondrially encoded subunits of the enzyme (2Walker J.E. Q. Rev. Biophys. 1992; 25: 253-324Crossref PubMed Scopus (685) Google Scholar, 18Chomyn A. Mariottini P. Cleeter M.W.J. Ragan C.I. Matsuno-Yagi A. Hatefi Y. Doolittle R.F. Attardi G. Nature. 1985; 314: 592-597Crossref PubMed Scopus (389) Google Scholar, 19Weiss H. Friedrich T. Hofhaus G. Preis D. Eur. J. Biochem. 1991; 197: 563-576Crossref PubMed Scopus (434) Google Scholar). Cross-linking studies on bovine complex I have shown, among other things, that only the 51-kDa subunit of FP (containing FMN and one iron-sulfur cluster) cross-links to only the 75-kDa subunit of IP (the only IP subunit that contains iron-sulfur clusters) (20Yamaguchi M. Hatefi Y. Biochemistry. 1993; 32: 1935-1939Crossref PubMed Scopus (32) Google Scholar). The interaction of these two subunits was confirmed by ligand blotting, which also showed that IP binds to the 42-, 39-, 23-, 20-, and 16-kDa subunits of HP (21Belogrudov G.I. Hatefi Y. Biochem. Biophys. Res. Commun. 1996; 227: 135-139Crossref PubMed Scopus (9) Google Scholar). In addition, we found that treatment of complex I with NAD(P)H, but not with NAD(P), altered the extent of cross-linking among the FP subunits, between the 51- and the 75-kDa subunits, among the IP subunits, and between the IP and the HP subunits (22Belogrudov G. Hatefi Y. Biochemistry. 1994; 33: 4571-4576Crossref PubMed Scopus (108) Google Scholar). This report presents data on the effects of NAD(H) and NADP(H) on the degradation of bovine complex I subunits by trypsin. In addition, it shows that in the presence of NADPH, but not NADP or NAD(H), the tryptic digestion of the 39-kDa subunit is arrested after comminution to a 33-kDa product. The significance of these results is discussed in relation to (a) redox-induced conformation changes of complex I as a possible mechanism for energy transduction, and (b) the possible role of certain complex I subunits in intramitochondrial fatty acid synthesis. NAD, NADH, NADP, and NADPH were from Calbiochem. TPCK-treated trypsin was from Sigma. Asolectin was from Associated Concentrates. Rotenone was from S. B. Penick and hexaammineruthenium chloride from Strem Chemicals. Complex I was isolated as described previously (23Hatefi Y. Methods Enzymol. 1978; 53: 11-14Crossref PubMed Scopus (189) Google Scholar). NADP-agarose (type I) was prepared by the method of Mosbach et al. (24Mosbach K. Guilford H. Ohlsson R. Scott M. Biochem. J. 1972; 127: 625-631Crossref PubMed Scopus (157) Google Scholar). Ubiquinone-1 (Q1) was a gift from Eisai Chemical (Tokyo, Japan). Polyclonal antibodies against the purified subunits of complex I were raised and affinity-purified as reported previously (25Han A.-L. Yagi T. Hatefi Y. Arch. Biochem. Biophys. 1988; 267: 490-496Crossref PubMed Scopus (28) Google Scholar, 26Han A.-L. Yagi T. Hatefi Y. Arch. Biochem. Biophys. 1989; 275: 166-173Crossref PubMed Scopus (43) Google Scholar). NADH-ubiquinone-1 reductase and NADH-K3Fe(CN)6 reductase activities of complex I were assayed as described elsewhere (23Hatefi Y. Methods Enzymol. 1978; 53: 11-14Crossref PubMed Scopus (189) Google Scholar). NADH-ubiquinone-1 reductase activity was assayed at 37 °C in a reaction mixture containing 20 mm potassium phosphate, pH 8.0, 0.1 mmubiquinone-1, 0.15 mm NADH, 2 mmNaN3, 200 μg of a suspension of asolectin clarified by sonication, and 4 μg of complex I. Specific activity was calculated using an extinction coefficient of 6.22 mm−1cm−1 for NADH at 340 nm. NADH-Ru(NH3)6Cl3 reductase activity was assayed at 37 °C in a reaction mixture containing 40 mm Tris-HCl, pH 7.5, 2 mmRu(NH3)6Cl3, 0.5 mmNADH, and 4 μg of complex I (27Sled' V.D. Vinogradov A.D. Biochim. Biophys. Acta. 1993; 1141: 262-268Crossref PubMed Scopus (63) Google Scholar). NADH oxidation was at 340 and activity was calculated as NADH-K3Fe(CN)6 reductase activity was assayed at 37 °C in a reaction mixture containing 40 pH 7.5, mm 0.15 mm NADH, and 2 μg of complex I. Specific activity was calculated using an extinction coefficient of for at nm. Complex I was with TPCK-treated trypsin complex I at °C in pH 8.0, containing and in the or the presence of as indicated in the the indicated of the reaction mixture were and with of trypsin to further of this mixture were used for of the enzyme activities and analysis of the digestion pattern of complex I by SDS-polyacrylamide gel electrophoresis and with were by the of an of buffer mm Tris-HCl, pH and by in for 4 to SDS-polyacrylamide gel electrophoresis Nature. 227: PubMed Scopus Google Scholar). were to using a The buffer 20 mm pH 1 mm and was at for 1 were with in a buffer containing 20 mm Tris-HCl, pH mm and 20 for 1 and for another 1 with the affinity-purified antibodies in containing The were three with and for 1 with The were with and were with the Complex I was with trypsin for 40 in the presence of 3 mm NADPH, trypsin was and the was in a at for of the and were in buffer and to SDS-polyacrylamide gel were and with affinity-purified antibodies to the to 39-kDa subunit, as described Complex I was with trypsin in the presence of 3 mm NADPH for 40 The was as described against of mm phosphate, pH containing 1 mm and the was to a 4 of The was with of the eluted with 5 of the buffer containing 1 mm NADPH, and with of the were and of was and to SDS-polyacrylamide gel were and with affinity-purified antibodies against the 39-kDa Complex I μg of with 2 μg of trypsin in the presence of 3 was to SDS-polyacrylamide gel electrophoresis and to membrane P. J. Biol. Chem. Full Text PDF PubMed Google Scholar) as described The membrane was with a mixture of and and and the 33-kDa from the 39-kDa subunit of complex I was for amino acid analysis of the was with an protein at the protein of this The protein was by the method of et al. as by Biochem. PubMed Scopus Google Scholar) or by the method J. Biol. Chem. Full Text PDF PubMed Google Scholar), using bovine as a The of bovine complex I used in these studies reduced by NADH at a of at 37 This activity was by the of trypsin on the degradation of complex I subunits in the or the presence of it was to complex I at 2 by the of the reduced the reductase activity of complex I to 7 and to of this mixture at °C with trypsin the of as in This indicated that the degradation of complex I subunits by trypsin the FP, to electron transfer from NADH to Q1, which is a that the activity of FP is not by trypsin these is also in It is that the activity of complex or its FP for electron transfer from NADH to or hexaammineruthenium chloride was after of with trypsin C.I. Biochem. J. PubMed Scopus Google Scholar, C.I. Biochem. PubMed Scopus Google Scholar). The pattern of complex I subunits to by trypsin is with these of on the digestion of complex I subunits by trypsin. Complex I at 2 was for 40 at °C with trypsin in the or the presence of 3 mm of NAD NADH NADP or NADPH 1 is a in the of trypsin and further digestion by the of trypsin μg of were to SDS-polyacrylamide gel and the gel was with and on the the subunits of complex I in and those in on the the of the The number on the is the molecular in of the product of the 39-kDa 2 shows on SDS-polyacrylamide gel the pattern of the subunits of complex I and after the treatment of complex I with trypsin in the and presence of 3 mm of NAD NADH NADP or NADPH The of the subunits by with antibodies are on the in and the of tryptic on the in in and the degradation of complex I subunits by trypsin was the in the and the presence of The 75-kDa subunit was the 51- and the subunits were to and and the 42-, 39-, and subunits were The subunit is not in but its degradation within the of 2 was by The results of 2 on the of trypsin on the and subunits of together with the data of 1 that the 51-kDa subunit was of the of NADH, and that the subunit was not for this The with the that the of E. coli (8Friedrich T. Steinmüller K. Weiss H. FEBS Lett. 1995; 367: 107-111Crossref PubMed Scopus (245) Google Scholar) and P. denitrificans (10Takano S. Yano T. Yagi T. Biochemistry. 1996; 35: 9120-9127Crossref PubMed Scopus (44) Google Scholar) not have a subunit to the mitochondrial subunit (20Yamaguchi M. Hatefi Y. Biochemistry. 1993; 32: 1935-1939Crossref PubMed Scopus (32) Google Scholar). In to the other subunits to which we not have antibodies were also by such as the two the 24-kDa subunit and the the The subunits and A. Mariottini P. Cleeter M.W.J. Ragan C.I. Matsuno-Yagi A. Hatefi Y. Doolittle R.F. Attardi G. Nature. 1985; 314: 592-597Crossref PubMed Scopus (389) Google Scholar) the of 2 gel to the showed that was and was by and the presence of on the extent of digestion by trypsin not In to NAD and NADP, which showed or on the digestion of complex I subunits by NADH and NADPH the trypsin susceptibility of the 75-kDa subunit, and NADPH, but not NADH, a 33-kDa digestion product of the 39-kDa subunit the on the in The of NADH on the tryptic digestion of the 75-kDa subunit is more in 3 2 and 3 This also shows that NADH the tryptic digestion of the and the subunits of IP, and 4 shows data for the 51- and 24-kDa subunits of FP and the 23-kDa subunit of In addition, NADH the tryptic degradation of the subunit of IP, but had on the digestion of the and the subunits, which on SDS-polyacrylamide as two In the NADPH the tryptic digestion of complex I subunits in a to NADH, that it is of complex I that its conformation and certain subunits more to by of NADH on the tryptic digestion of complex I subunits with molecular masses of 51, 24, and I was with trypsin as described in 2 in the or the presence of 3 mm 1 are complex I. electrophoresis and transfer to the were with affinity-purified antibodies to the 51-kDa and the 24-kDa subunits of the FP and the 23-kDa subunit of the HP other to the was the of NADPH on the 39-kDa subunit of complex I. in NAD, NADP, and NADH had on the tryptic digestion of the 39-kDa subunit, the presence of NADPH 6 and in the of a 33-kDa product that resisted further tryptic 5 shows that the of the 33-kDa product increased with the of NADPH in the digestion that the of the 33-kDa product against further was a of NADPH This with the data of and Walker (1Fearnley I.M. Walker J.E. Biochim. Biophys. Acta. 1992; 1140: 105-134Crossref PubMed Scopus (292) Google Scholar), that the of the 39-kDa subunit of the bovine and the subunit of the crassa complex I is a motif to the sequences of the 51-kDa subunit of bovine complex I. It was of to this was in the 33-kDa product of the 39-kDa the 33-kDa was to from of complex I with trypsin in the presence of NADPH, and to It was found that the amino of the 39-kDa subunit had been by trypsin at the the which of In this are two possible at and which were by the bound NADPH. the conformation of the NADPH bound 33-kDa the of other by trypsin as that the 33-kDa digestion product of the 39-kDa subunit was of complex I was with trypsin for 40 in the presence of 3 mm further digestion was arrested by the of trypsin and the mixture was to SDS-polyacrylamide gel electrophoresis and with affinity-purified antibodies against the 39-kDa subunit showed that both the 39-kDa subunit and its 33-kDa tryptic were between the and the 6 The was and on a NADP-agarose column, after with the the was eluted with the buffer containing 1 the 39-kDa and its 33-kDa tryptic were eluted these 6 that both polypeptides were of to NADP-agarose and of by a buffer containing NADPH. These results together with those of that the of the and the 39-kDa subunit are and only the conformation is to tryptic in the studies had shown that the cross-linking pattern of complex I subunits changes when the enzyme is reduced with NADH or NADPH. These changes involved the of subunits within FP and IP as well as between the FP and IP subunits and between the IP and HP subunits (22Belogrudov G. Hatefi Y. Biochemistry. 1994; 33: 4571-4576Crossref PubMed Scopus (108) Google Scholar). In the the data shown also that of complex I by NADH or NADPH increases the susceptibility to trypsin digestion of a number of the subunits found in the FP, IP, and HP of complex I. These extensive structural changes by of complex I may be an of the in the within the enzyme when it is or may be of significance and of conformation of the enzyme as a coupling mechanism for number of have been for by complex NADH, FMN, as the P. J. Biol. PubMed Scopus Google Scholar, C.I. Bioenerg. Scopus Google Scholar, G. J. Biol. Chem. 1988; Full Text PDF PubMed Google Scholar, H. Friedrich T. J. Bioenerg. Biomembr. 1991; PubMed Scopus Google Scholar, A.D. J. Bioenerg. Biomembr. 1993; 25: PubMed Scopus Google Scholar, U. Biochim. Biophys. Acta. 1997; PubMed Scopus Google Scholar). of these were by the of electron transfer and by complex J. Biol. Chem. 1990; Full Text PDF PubMed Google Scholar). is for of these of by complex and recent studies have of complex that be with the A. Hatefi Y. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google A. Hatefi Y. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). Furthermore, a mechanism be for the reductase R. P. Biochemistry. 1996; 35: PubMed Scopus Google Scholar) with the or the being the is in that energy conformation as a key step. In energy the conformation of to and the of a from the that to of the protein J. Bioenerg. Biomembr. 1992; PubMed Scopus Google Scholar). In ATP and the energy in the NADPH in the protein conformation changes that in Y. Eur. J. Biochem. 1993; PubMed Scopus (63) Google Scholar, Annu. Rev. Biochem. 1997; PubMed Scopus Google Scholar, Y. M. J. 1996; PubMed Scopus Google Scholar). energy is also protein conformation for by the M. J. Bioenerg. Biomembr. 1992; PubMed Scopus Google Scholar). it is possible that in complex I it is also the in are carriers. the energy is to protein conformation changes that in changes of amino acid residues and the and of the domain of the This is by that in electron transfer from succinate to NAD, as by submitochondrial the affinity of complex I for NAD increases ≥20-fold when the particles are energized by ATP Y. Yagi T. Galante Y.M. U. S. A. 1982; PubMed Scopus (40) Google Scholar). of described is the of NADPH on the tryptic degradation of the 39-kDa subunit of complex I. In this NADPH appears to to the 39-kDa subunit and results in the of a 33-kDa which further of the 33-kDa showed that it had the amino acid residues of the 39-kDa subunit, and a to it its it had the of which it of to the 33-kDa was also of NADPH and a conformation to trypsin These a the role of this 39-kDa but not subunit of complex I. It was shown in by this that complex I was also of NADPH which was at pH Y. Biochemistry. PubMed Scopus Google Scholar). results were with the FP of complex I Y. Galante Y.M. S. Hatefi Y. A. The of Membranes. Scholar). These as well as studies of complex I the that NADH and NADPH oxidation involved the complex I subunits and centers Y. Biochem. Biophys. Res. Commun. PubMed Scopus Google Scholar). This agreed with by that per mol of complex I is 1 mol of the and subunits of FP and the and subunits of IP (21Belogrudov G.I. Hatefi Y. Biochem. Biophys. Res. Commun. 1996; 227: 135-139Crossref PubMed Scopus (9) Google Scholar). These data not with the of and Biochim. Biophys. Acta. 1997; PubMed Scopus Google Scholar) that complex I contains for the of NADH and NADPH. may the 39-kDa subunit, which not to NADH, is the NADPH suggested by and Biochim. Biophys. Acta. 1997; PubMed Scopus Google Scholar). not the of complex I is with the 51-kDa subunit of we that the 39-kDa subunit be involved together with the acyl carrier protein subunit of complex I in fatty acid R. H. Schneider R. T. Weiss H. FEBS Lett. 1992; PubMed Scopus Google Scholar, R. M. T. Weiss H. 1995; 29: PubMed Scopus Google Scholar, R. B. M. Weiss H. FEBS Lett. 1997; PubMed Scopus Google Scholar, S. C. U. E. FEBS Lett. 1997; PubMed Scopus Google Scholar, S.W. J.E. J. Biol. Chem. 1997; Full Text Full Text PDF PubMed Scopus Google Scholar). C. for the of bovine mitochondria and