CRYSTALLIZATION OF INTACT AND SUBUNIT-L-DEFICIENT MONOMERS FROM SYNECHOCYSTIS PCC-6803 PHOTOSYSTEM-I

Photosystem I monomers from wildtype cells of Synechocystis PCC 6803 a nd from a mutant deficient in the psaL gene were crystallized. PsaL en codes for the hydrophobic subunit L, which has been proposed to consti tute the trimerization domain in the PS I trimer. The absence of subun it L facilitated crystallization of the PS I monomer. The unit cell di mensions and the space group for the crystals from this preparation co uld be determined to be a = b = 132 Angstrom, c = 525 Angstrom, alpha = beta = 90 degrees, gamma = 120 degrees, the space group is P6(1) or P6(5). The results show the potential of using specifically designed d eletion mutants of an integral membrane protein for the systematic imp rovement of crystal structure data.