Characterization of porins from the outer membrane of Salmonella typhimurium. 1. Chemical analysis.

摘要: The three species of channel-forming outer membrane proteins, porins, have been purified to homogeneity from mutant strains Salmonella typhimurium which produce single porin. Purification was by stepwise solubilization with dodecylsulfate or guanidine thiocyanate, gel filtration, and preparative electrophoresis. Amino acid compositions tryptic peptide maps the porins showed close resemblance, but at same time clear differences among them. number amino residues in SH5551, SH6377 SH6017 were 361, 354 345, their calculated molecular weights 39800, 39300 38000, respectively. Amino-terminal carboxyl-terminal acids all appeared be alanine phenylalanine, Neither half-cystine nor hexosamine found these preparation porins. isoelectric points SH6017, determined focusing, slight each other. These results, genetic experiments another laboratory, suggest that are distinct polypeptides, probably coded for structural genes, might derived ancestral gene.