| Abstract: | The complete amino acid sequence of cytosolic adenylate kinase (MgATP + AMP----MgADP + ADP) from baker's yeast has been determined. Tryptic and clostripaic cleavage of the protein yielded 27 and 10 fragments, respectively. They were sequenced with either a solid-phase sequencer or a gas-phase sequencer. Alignment of the clostripaic fragments was deduced from the sequence of peptides obtained by endoproteinase Lys-C and cyanogen bromide cleavages. The N-terminus is blocked by an acetyl group as shown by proton magnetic resonance. Carboxypeptidase A digestion of the whole protein showed that the C-terminal sequence is -Lys-Asn, in agreement with the sequence of peptides from tryptic, clostripaic and 2-iodosobenzoic acid cleavages. The enzyme is a monomer of 220 amino acids with Mr 24077. Comparison of the sequence of the cytosolic adenylate kinases from yeast and pig shows 25% identity with highly conserved segments in the putative active-site region of the enzyme. After position 111, however, there is an insertion of 32 residues in the yeast species, similar to the adenylate kinase and the GTP:AMP phosphotransferase from beef heart mitochondria. |
