title: The primary structure of subunit II of NADH dehydrogenase from bovine-heart mitochondria.
abstract: Subunit II (with a molecular mass of about 24000 dalton, approximately 24 kDA) of NADH dehydrogenase from beef heart mitochondria was [ 14C ]carboxymethylated and cleaved with CNBr and proteolytic enzymes. Sequence analyses of purified fragments suggest that the subunit is composed of a homogeneous polypeptide chain, containing just over 230 residues. The primary structure of this chain was established except for a 14-residue internal part which was only determined by composition. The amino acid sequence suggests that four cysteine residues are involved in the binding of an iron-sulfur cluster. The subunit contains no long hydrophobic segment, in contrast to structures often found in membrane proteins, but in agreement with a model where the functional unit of NADH dehydrogenase in the membrane is shielded by other intra-membrane proteins. The polypeptide has a weak similarity to the iron-sulfur binding region of ferredoxin and has interesting but possibly insignificant similarities to parts of previously compared flavin-linked enzymes.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002621:Chemistry; D003545:Cysteine / Q000032:analysis; D003579:Cytochrome Reductases / Q000302:isolation & purification*; D007506:Iron-Sulfur Proteins; D008929:Mitochondria, Heart / Q000201:enzymology*; D009245:NADH Dehydrogenase / Q000302:isolation & purification*; D010446:Peptide Fragments / Q000302:isolation & purification
chemical_list: D007506:Iron-Sulfur Proteins; D010446:Peptide Fragments; D003579:Cytochrome Reductases; D009245:NADH Dehydrogenase; D003545:Cysteine