title: Haemophilus influenzae penicillin-binding proteins 1a and 3 possess distinct and opposite temperature-modulated penicillin-binding activities.
abstract: Upon investigation of penicillin-binding proteins (PBPs) in Haemophilus influenzae strains, five H. influenzae and seven other Haemophilus strains were tested for whole-cell penicillin binding at either 37 or 42 degrees C. Binding of [35S]penicillin G to H. influenzae PBPs 3a and 3b was drastically reduced at 42 degrees C, while PBP 1a showed a temperature-modulated increase in penicillin binding. Further investigation revealed that growth at 42 degrees C causes altered electrophoretic mobility of PBP 3a on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and that cell labeling performed at 42 degrees C showed the differential penicillin binding to target proteins. All Haemophilus spp. tested showed a similar temperature modulation of penicillin binding. Growth measurement and cell viability studies performed at 42 degrees C permitted correlation of PBP 3 temperature sensitivity to H. influenzae resistance to moxalactam at 42 degrees C, and the probable correlation of PBP 1a increased penicillin binding to the more rapid antibacterial activity of penicillin G against H. influenzae at 42 degrees C. Microscopic examination of Haemophilus cells grown at 42 degrees C revealed filamentous cell formation, supporting a role of PBP 3 in the septation process. Results of this study demonstrate that wild-type H. influenzae strains (and possibly all other Haemophilus spp.) possess PBPs 1a and 3, which have distinct and opposite temperature-modulated penicillin-binding activities.
authors.affiliation: Department of Microbiology and Infectious Diseases, University of Calgary Health Sciences Centre, Alberta, Canada.
authors.forename: F
authors.initials: F
authors.lastname: Malouin
authors.forename: L E
authors.initials: LE
authors.lastname: Bryan
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006190:Haemophilus / Q000254:growth & development / Q000378:metabolism; D006193:Haemophilus influenzae / Q000254:growth & development / Q000378:metabolism*; D006602:Hexosyltransferases / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000378:metabolism*; D002267:Muramoylpentapeptide Carboxypeptidase; D010400:Penicillin G / Q000378:metabolism*; D046915:Penicillin-Binding Proteins; D010458:Peptidyl Transferases / Q000378:metabolism*; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D009097:Multienzyme Complexes; D046915:Penicillin-Binding Proteins; D000217:Acyltransferases; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; D010400:Penicillin G