ISOLATION AND CHARACTERIZATION OF PORIN FROM THE OUTER-MEMBRANE OF SYNECHOCOCCUS PCC-6301

Pore-forming protein (porin) was isolated from N,N-dimethyl-dodecylami noxid (LDAO)-extracted outer membranes of Synechococcus PCC 6301 and p urified by ion exchange chromatography on DEAE-Sephacel column. The ap parent molecular mass on SDS-PAGE was determined to be about 52000. Th e native porin was reconstituted into black lipid bilayer membranes an d showed a single-channel conductance of 5.5 nS in 1 M KCl. The porin was found to be N-terminally blocked. The C-terminal amino acid sequen ce was identified as Phe-Thr-Phe. Amino acid analysis suggested that t he porin protein consists of about 420 amino acid residues, yeilding a polarity of 43.6% and a molecular mass of 45000 in contrast to the mo bility on SDS-PAGE.