The 49 K subunit of NADH: ubiquinone reductase (complex I) from Neurospora crassa mitochondria: primary structure of the gene and the protein

Abstract

The primary structure of the 49 K subunit of the respiratory chain NADH:ubiquinone reductase (complex I) from Neurospora crassa was determined by sequencing cDNA, genomic DNA and the N-terminus of the mature protein. The sequence lengths correlate to a molecular mass of 54,002 daltons for the preprotein and 49,239 daltons for the mature protein. The presequence consists of 42 amino acids of typical composition for sequences which target nuclear-encoded proteins into mitochondria. The mature protein consists of 436 amino acids and shows 64% similarity to a 49 K subunit of bovine heart NADH:ubiquinone reductase and 33% to a predicted translation product of an open reading frame in the chloroplast DNAs of Marchantia polymorpha and Nicotiana tabacum. Evidence for an iron-sulfur cluster in the subunit is discussed.

The respiratory‐chain NADH dehydrogenase (complex I) of mitochondria

“…The nuclear-encoded 75-kDa, 49-kDa and 40-kDa subunits are very susceptible to proteolysis and several smaller degradation products of these subunits are often found, especially in preparations of the small form of NADH dehydrogenase which is isolated from the chloramphenicol-poisoned N . crassa hyphae (see also [25,261) Bacterial cytochrome reductases and cytochrome oxidases have been known for many years to be composed of considerably fewer subunits than their eucaryotic counterparts, but to be related in terms of the subunits carrying the redox centres [28 -301. NADH …”

“…All subunits for which we know the sequences are listed in Table 1 [25,26,47,. We propose to classify them according to their location in the two parts of NADH dehydrogenase (Fig.…”

“…Three cysteines spaced as Cys(Xaa), Cys(Xaa)l,Cys are conserved between bovine [59] and N . crassa [25]. These cysteines are, however, not found in a translation product deduced from an open reading frame in the chloroplast genome of Marchantiapolymorpha [lo21 and Nicotiana tabacum [lo31 which exhibit some 30% sequence identity [104], see also Fig.…”

Studies on the expression of NDH-H, a subunit of the NAD(P)H-plastoquinone-oxidoreductase of higher-plant chloroplasts

“…The mitochondrial counterpart to NDH-H had been known before as the 49-kDa subunit. The protein is localized in the so-called iron-sui fur protein fragment or the peripheral arm of complex I, referring to the old (Hatefi 1985;Ragan 1987) and the new (Weiss et al 1990) model of the enzyme, repectively. Table 1 shows a sequence analysis of the NDH-H proteins of different organisms.…”

Mitochondrial Expression and Function of GAS-1 in Caenorhabditis elegans

“…proton-pumping across the mitochondrial membrane, driven by the transfer of electrons from NADH to a quinone (9 -10). A knockout mutant of the "49-kDa(IP) gene" in Neurospora completely lacked NADH-dehydrogenase activity, because the "matrix arm" of the enzyme complex failed to assemble (11). All of the Complex I mutants in Neurospora were reported to have reduced growth rates, and their conidia were less viable.…”