cotA of Synechocystis sp. strain PCC6803 is a gene involved in light-induced proton extrusion (A. Katoh, M. Sonoda, H. Katoh, and T. Ogawa, J. Bacteriol. 178:5452-5455, 1996). There are two possible initiation codons in cotA, and either long (L-) or short (S-) cotA encoding a protein of 440 or 247