Characterization of two pore-forming proteins isolated from the outer membrane of Synechococcus PCC 6301.
Two major proteins, A and B, were isolated and purified from outer membranes of the unicellular cyanobacterium Synechococcus PCC 6301 by gel filtration, anion-exchange chromatography, and preparative SDS-PAGE. Protein A revealed a single-channel conductance of 0.4 nanoSiemens (nS) in 1 M KCl, whereas preparations containing both proteins showed two different conductance maxima of 0.4 and 0.9 nS, suggesting that B also forms pores. The apparent molecular mass of the two closely migrating proteins was determined as 52 kDa, whereas native porin extracts revealed a relative molecular mass of ca. 140 kDa, indicating trimeric pore-forming units. Partial sequences of both proteins were obtained by N-terminal sequencing of tryptic peptides, and the C-terminal amino acid sequences were derived from the complete proteins. These sequences were aligned to protein sequences available in the databases. The results are discussed.
Hansel
A
A
Institut für Biologie II, Mikrobiologie, Albert-Ludwigs-Universität, Freiburg, Germany.
Tadros
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MH
D000595:Amino Acid Sequence; D000458:Cyanobacteria / Q000737:chemistry*; D008969:Molecular Sequence Data; D018272:Porins / Q000737:chemistry / Q000302:isolation & purification*
D018272:Porins