Resolution of the Membrane Domain of Bovine Complex I into Subcomplexes:  Implications for the Structural Organization of the Enzyme

Abstract

Complex I (NADH:ubiquinone oxidoreductase) purified from bovine heart mitochondria was treated with the detergent N, N-dimethyldodecylamine N-oxide (LDAO). The enzyme dissociated into two known subcomplexes, Ialpha and Ibeta, containing mostly hydrophilic and hydrophobic subunits, and a previously undetected fragment referred to as Igamma. Subcomplex Igamma contains the hydrophobic subunits ND1, ND2, ND3, and ND4L which are encoded in the mitochondrial genome, and the nuclear-encoded subunit KFYI. During size-exclusion chromatography in the presence of LDAO, subcomplex Ialpha lost several subunits and formed another characterized subcomplex known as Ilambda. Similarly, subcomplex Ibeta dissociated into two smaller subcomplexes, one of which contains the hydrophobic subunits ND4 and ND5; subcomplex Igamma released a fragment containing ND1 and ND2. These results suggest that in the intact complex subunits ND1 and ND2 are likely to be in a different region of the membrane domain than subunits ND4 and ND5. The compositions of the various subcomplexes and fragments of complex I provide an organization of the subunits of the enzyme in the framework of the known low resolution structure of the enzyme.

High frequency of mitochondrial DNA mutations in glioblastoma multiforme identified by direct sequence comparison to blood samples

“…The mutation replaces a large hydrophobic phenylalanine residue in the NADH dehydrogenase 5 polypeptide (complex I) by a small serine residue. Since ND5 is a hydrophobic subunit of the membrane domain of complex I, 22 functional relevance of the substitution cannot be excluded. However, the phenylalanine residue is conserved only among primates and not among other mammals and birds according to the Genbank database.…”

Inactivation of genes coding for mitochondrial Nd7 and Nd9 complex I subunits in Chlamydomonas reinhardtii. Impact of complex I loss on respiration and energetic metabolism

“…In human, the NADH dehydrogenase module (comprising notably NDUFV2/24 kD, NDUFV1/51 kD and NDUFS1/75 kD) is distinct from the hydrogenase module (comprising notably NDUFS3/Nd9, NDUFS2/Nd7, NDUFS7/PSTT, NDUFS8/TYKY) and these two fractions (fractions FP and IP, respectively, e.g. Sazanov et al, 2000) are assembled separately (Antonicka et al, 2003;Vogel et al, 2007). In NUO7 and NUO9 knockdown Chlamydomonas mutants, while we found the soluble ~200 kD NADH dehydrogenase activity along with the 75 kD (NDUFS1) subunit detected in membrane extract (data not shown), subunits NDUFS7/PSTT, NDUFS8/TYKY of the hydrogenase module are absent.…”

NDUFA10 mutations cause complex I deficiency in a patient with Leigh disease

“…31,32 Furthermore, it has been described that unlike other protein components of the membrane arm, NDUFA10 is a relatively hydrophilic protein and is thought to be generally weakly associated with complex I. 33,34 The phosphorylation might influence the binding affinity of NDUFA10 and regulate the amount of fully-active complex. In addition, the loose association of the NDUFA10 subunit would make it more accessible to external interactions with other proteins like kinases and phosphatases.…”