Expression of the chloroplast atpB gene of Chlamydomonas reinhardtii in E. coli

Energy derived from electron transport in mitochondrial, chloroplast thylakoids and bacterial plasma membranes is transduced to form ATP by the F1·F0 proton translocating ATP synthases1. These enzyme complexes are composed of an intrinsic membrane protein complex, F0, which mediates H+-translocation, and a peripheral protein complex, F1, which catalyzes the terminal step of synthesis of ATP from ADP and Pi. F1 is composed of five different polypeptide chains designated α-ε in order of decreasing Mr with a subunit stoichiometry of α3β3γδε. The binding sites for ADP and ATP are located on the α and β subunits and the catalytic sites are thought to be on the β subunits. Isolated CF1 is a latent ATPase which can be activated by a variety of means to exhibit a Mg2+- or a Ca2+- dependent ATPase activity (1). Subunits α, β and ε of CF1 are encoded in the chloroplast DNA (2,3). The gene atpB from chloroplast DNA of Chlamydomonas reinhardtii, encoding for subunit β, was isolated and sequenced (4). We have subcloned the atpB gene into pT7-2 from plasmid pB7 (a gift from Dr. N. Gillham). RNA from this plasmid was transcribed and translated in vitro. The β subunit synthesized in vitro was shown to assemble into CF1 (5).