title: Secretion of a 107 K dalton polypeptide into the medium from a haemolytic E. coli K12 strain.
abstract: Certain E. coli K12 strains are able to secrete a plasmid encoded 107 K protein into the culture medium. During exponential growth of the cells this protein represents approximately 1% of total cell protein. The presence of the 107 K polypeptide was demonstrated through the fortuitous use of strain MC4100. This gave a largely protein-free culture supernatant, presumably due to minimal lysis of whole cells. Pulse-labelling experiments showed that the secretion of the 107 K polypeptide reached a maximum during the stationary phase of growth, where it represented substantially more than 1% of total cell protein. The 107 K polypeptide is coded by the haemolytic plasmid pHly167, and appears to be related to a previously reported intracellular "precursor" form of the alpha-haemolysin (Goebel and Hedgpeth 1982). However, additional extracellular factors appear to be required for alpha-haemolysin activity since several nonhaemolytic mutants still secrete this protein.
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D006461:Hemolysis; D007700:Kinetics; D008970:Molecular Weight; D010957:Plasmids; D013045:Species Specificity
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements