The 42.5 kDa subunit of the NADH: ubiquinone oxidoreductase (complex I) in higher plants is encoded by the mitochondrial nad7 gene

Abstract

The N-terminal amino acid sequence of a 42.5 kDa subunit of the NADH: ubiquinone oxidoreductase (complex I) from potato has been determined by direct protein sequencing. The sequence was found to be homologous to that of the nuclear-encoded 49 kDa complex I subunit of bovine and Neurospora mitochondria and to the sequence deduced from the mitochondrial nad7 gene identified in the mitochondrial (mt) DNA of tryp anosomes and the moss Marchantia. An oligonucleotide probe derived from the potato N-terminal protein sequence hybridized only to the plant mtDNA. Immunoprecipitation of in-organello 35S-labelled potato and wheat mitochondrial translation products with an antibody directed against the Neurospora 49 kDa complex I subunit indicates that at least in these plants the NAD7 protein is synthesized within the organelle. Comparisons of genomic, cDNA and protein sequences of the 5' coding region reveal three codons that are changed by RNA-editing and confirm translation of the edited transcripts in plant mitochondria. The NAD7 protein appears to undergo post-translational processing since the N-terminal methionine residue is absent from the mature mitochondrial protein.

Analysis of the Iron‐Sulfur Clusters Within the Complex I (NADH: Ubiquinone Oxidoreductase) Isolated from Potato Tuber Mitochondria

“…These subunits are in particular the 75-kDa, 51-kDa, 24-kDa, 23-kDa (bovine TYKY), and 20-kDa (bovine PSST) complex I proteins . Plant mitochondrial genomes are much larger in size and appear to contain two more genes coding for complex I subunits (the homologues of the nuclear-encoded bovine 49-kDa and 30-kDa proteins; Oda et al, 1992: Lamattina et al, 1993Gabler et al, 1994;. However, all putative iron-sulfur proteins of the plant complex I are, as in mammals and fungi, encoded by nuclear genes and show a high degree of sequence conservation in their primary structures, in particular of the cysteine-rich sequence stretches which are proposed as the FeS-cluster binding sites (Grohmann et al, 1995).…”

Peptide deformylase as a target for new generation, broad spectrum antimicrobial agents

“…Similar sequences were also identified in higher plants ( Arabidopsis thaliana , tomato, corn, and rice; C. Giglione, M. Pierre and T. Meinnel, unpublished results). Deformylation has been shown to occur in some algal chloroplasts (see quoted in Meinnel, 2000) and in various plant mitochondria (Braun and Schmitz, 1993; Gabler et al ., 1994; Herz et al ., 1994) and chloroplasts (Hauska et al ., 1988; Schmidt et al ., 1992; Shanklin et al ., 1995). It therefore seems likely that these PDF are targeted to the mitochondria or plastids by an N‐terminal exportation presequence.…”

The 28.5-kDa iron-sulfur protein of mitochondrial complex I is encoded in the nucleus in plants

“…Three additional genes (nad7-nad9) encoding complex I proteins have been found on the mitochondrial maxicircle DNA of trypanosomes (Koslowsky et al 1990;Souza et al 1992). Recently, two homologous genes (nad7 and nad9) coding for complex I proteins have also been identified in the mitochondrial genomes of plants, i.e., wheat and potato (Lamattina et al 1993;Bonen et al 1994;Ga¨bler et al 1994;Grohmann et al 1994). The large size of plant mitochondrial genomes (250-2500 kb) suggests by extrapolation that additional complex I subunits may be encoded mitochondrially.…”