AN INVESTIGATION INTO THE ABILITY OF C-TERMINAL HOMOLOGS OF ESCHERICHIA-COLI LOW-MOLECULAR-MASS PENICILLIN-BINDING PROTEIN-4, PROTEIN-5 ANDPROTEIN-6 TO UNDERGO MEMBRANE INTERACTION

The Escherichia coli low molecular mass penicillin-binding proteins (P BP4, PBP5 and PBP6) are a group of penicillin-sensitive enzymes involv ed in the final stages of cell wall assembly. It has been suggested th at these proteins may interact with the periplasmic face of the inner membrane via C-terminal amphiphilic a-helices. Theoretical analysis ha s predicted that these C-terminal helical regions may be membrane inte ractive. We have tested this hypothesis by assaying PBP C-terminal hom ologues (P4, P5 and P6) for haemolytic activity. Our results show that the PBP5 and PBP6 C-terminal homologues readily lyse sheep erythrocyt es in a pi-I-dependent manner with LD50's of 3.5 x 10(-6) M and 6.8 x 10(-7) M respectively at pH 7. These results appear to support the pre sent model for the membrane anchoring of PBP5 and PBP6. The PBP4 C-ter minal homologue shows no evidence of haemolytic activity which could i mply a different means of membrane association for PBP4.