The primary structure of the γ‐subunit of the ATPase from Synechocystis 6803

Abstract

The nucleotide sequence of the gene coding for the F,F,-ATPase y-subunit (arpC) from the transformable cyanobacterium Synechocystis 6083 has been determined. The deduced translation product consists of 314 amino acid residues and is highly homologous (72% identical residues) to the sequences of other cyanobacterial y-subunits. The Synechocystis 6803 sequence is also homologous to the chloroplast y-sequence. Like in the other cyanobacterial subunits, only the first of the 3 cysteine residues, which are involved in energy-linked functions of the y-subunit in spinach chloroplasts, is conserved in Synechocystis 6803.

The Ferredoxin/Thioredoxin System of Oxygenic Photosynthesis

“…The role of this regulatory element has been confirmed by introduction of mutations into the sequence motif (230,231) and by insertion of the regulatory element into the ␥-subunit of a cyanobacterial, thiol-insensitive CF 1 (296). This motif, which is contained in an extra peptide, is present in the enzyme of land plants (190) and green algae (308) but not in the counterpart of cyanobacteria (48,179,295), diatoms (207), or mitochondria. Recent results indicate that the interaction between the ␥-and -subunits is important for redox regulation (146).…”

“…In organisms such as cyanobacteria in which CF 1 serves a dual function in oxidative and photophosphorylation, the enzyme should remain active in the dark. Thus, in such organisms, CF 1 lacks the regulatory disulfide segment seen with the chloroplast counterpart (48,179,295).…”

Plant Thioredoxin Systems Revisited

“…The γ subunit of the latter contains the structural element, which allows for thiol modulation of the enzyme by Trx f (108, 141). The regulatory motif-Cys199AspIleAsnGlyLysCys205 in spinach (Table 1)-is present in the subunit from plants (97) and green algae (32), but is absent in the enzyme of cyanobacteria (32,95,163) and diatoms (109) or mitochondrial F 1 . The disulfide bridge between the two Cys residues seems to be inaccessible in the inactive enzyme in the dark and becomes exposed upon activation by the transmembrane electrochemical proton gradient (35b).…”

A Conformational Change of the γ Subunit Indirectly Regulates the Activity of Cyanobacterial F1-ATPase

“…Compared with the bacterial and mitochondrial F 1 -␥, the ␥ subunit of cyanobacterial F 0 F 1 also bears the inserted sequence like spinach CF 1 -␥, although the sequence lacks nine amino acids including two regulatory Cys residues for redox regulation (31). In our previous studies, the mutant ␣ 3 ␤ 3 ␥ complex was prepared in which the ␥ insertion sequence of cyanobacterium Thermosynechococcus elongatus BP-1 F 1 was deleted (25,32).…”