SEC-Y PROTEIN IS LOCALIZED IN BOTH THE CYTOPLASMIC AND THYLAKOID MEMBRANES IN THE CYANOBACTERIUM SYNECHOCOCCUS PCC7942

Members of the SecY protein family mediate protein export in bacterial cells. Southern analyses showed that secY is likely a single copy gene in the cyanobacterium Synechococcus PCC7942. Then the subcellular location of the cyanobacterial SecY protein was determined; i) antiserum raised against a fusion protein between the SecY fragment and maltose binding protein were used for immunoblotting of the membrane fractions, and ii) a modified SecY protein carrying the c-Myc peptide tag was expressed in the cyanobacterial cells, and the subcellular distribution of the SecY-c-Myc fusion protein was analyzed with the anti-c-Myc antibodies. The obtained results suggest that the SecY protein is localized in the thylakoid membrane as well as the cytoplasmic membrane; the SecY protein probably mediates protein translocation across both the cytoplasmic and thylakoid membranes in Synechococcus PCC7942. © 1993 Academic Press.