Expression of the wheat chloroplast gene for CF0 subunit IV of ATP synthase

The nucleotide sequence of the wheat chloroplast atp I gene encoding CF0 subunit IV of ATP synthase has been determined. The gene encodes a polypeptide of 247 amino acid residues with high sequence similarity to subunit IV from other plant chloroplasts and from cyanobacteria. The polypeptide shows sequence homology to the C-terminus of the F0 alpha subunit of Escherichia coli ATP synthase and subunit 6 of mitochondrial ATP synthase. The atp I gene is co-transcribed with the atp H, atp F and atp A genes for other subunits of ATP synthase in wheat. A gene-fusion of most of the atp I coding region with cro'-lacI'-lacZ' has been constructed in pEX2 and the fusion-protein has been used to raise antibodies in rabbits. The antibodies react with a polypeptide of 17 kDa in wheat thylakoid membranes indicating that the wheat atp I gene is expressed at the protein level. A model for the organisation of the polypeptide in the thylakoid membrane with four membrane-spanning segments is proposed.