title: Integration of the Serratia marcescens haemolysin into human erythrocyte membranes.
abstract: The haemolytic activity of Serratia marcescens is determined by two proteins, ShlA and ShlB. ShlA integrates into the erythrocyte membrane and causes osmotic lysis through channel formation. The conformation of ShlA and its interaction with erythrocyte membranes were studied by determining the cleavage of ShlA by added trypsin. Our results suggest that the conformation of inactive ShlA (from an ShlB- strain) differs from the active ShlA, and that in a hydrophobic environment (detergent or membrane) active ShlA assumes a conformation distinct from that in buffer. Only active haemolysin adsorbed to erythrocytes. ShlA was firmly integrated into the erythrocyte membrane since it was only released under conditions which also dissolved the integral erythrocyte membrane proteins. Moreover, ShlA integrated into 'ghosts' remained there and was not haemolytic when incubated with erythrocytes. From the trypsin cleavage pattern obtained with haemolysin and C-terminally truncated, but still active, haemolysin derivatives integrated into erythrocytes, and sealed and unsealed erythrocyte 'ghosts', we conclude that ShlA is preferentially cleaved by trypsin at a few sites but only from the inside of the erythrocyte. Haemolysin in the erythrocyte membrane forms a water-filled channel and is resistant to trypsin and other proteases.
authors.affiliation: Mikrobiologie II, Auf der Morgenstelle 28, Universität Tübingen, FRG.
authors.forename: E
authors.initials: E
authors.lastname: Schiebel
authors.forename: V
authors.initials: V
authors.lastname: Braun
mesh_terms: D000042:Absorption; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D004910:Erythrocyte Membrane / Q000378:metabolism*; D006460:Hemolysin Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D008956:Models, Chemical; D011487:Protein Conformation; D012706:Serratia marcescens / Q000378:metabolism*; D014357:Trypsin
chemical_list: D001426:Bacterial Proteins; D006460:Hemolysin Proteins; D008565:Membrane Proteins; D014357:Trypsin