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Escherichia colilow molecular mass penicillin-binding pro-teins (PBPs) include PBP4, PBP5, PBP6 and PBP6b. Evi-dence suggests that these proteins interact with the inner membrane via C-terminal amphiphilica-helices. Nonethe-less, the membrane interactive mechanisms utilized by the C-terminal anchors of PBP4 and PBP6b showdifferences to those utilized by PBP5 and PBP6. Here, hydrophobic moment-based analyses have predicted that, in contrast to the PBP4 and PBP6b C-termini, those of PBP5 and PBP6 are candidates to form oblique orientateda-helices | Eur. J. Biochem. 269 5821-5829 2002 FEBS 2002 doi 10.1046 j.1432-1033.2002.03295.x Investigations into the mechanisms used by the C-terminal anchors of Escherichia coli penicillin-binding proteins 4 5 6 and 6b for membrane interaction Frederick Harris1 Klaus Brandenburg2 Ulrich Seydel2 and David Phoenix1 1 Department of Forensic and Investigative Science University of Central Lancashire Preston UK 2Division of Biophysics Forschunginstitute Borstel Borstel Germany Escherichia coli low molecular mass penicillin-binding proteins PBPs include PBP4 PBP5 PBP6 and PBP6b. Evidence suggests that these proteins interact with the inner membrane via C-terminal amphiphilic a-helices. Nonetheless the membrane interactive mechanisms utilized by the C-terminal anchors of PBP4 and PBP6b show differences to those utilized by PBP5 and PBP6. Here hydrophobic moment-based analyses have predicted that in contrast to the PBP4 and PBP6b C-termini those of PBP5 and PBP6 are candidates to form oblique orientated a-helices. Consistent with these predictions. Foil net transfonn in Irared spectroscopy FTIR has shown that peptide homologs of the PBP4 and PBP5 C-terminal regions P4 and P5 respectively bothpossessed the ability to adopt a-helical structure in the presence of lipid. However whereas P4 appeared to show a preference for interaction with the surface regions of dimyristoylglycerophosphoethanolamine and dimyristoylglycerophosphoglycerol membranes P5 appeared to show deep penetration of both these latter membranes and dimyristoylglycerophosphocholine membranes. Based on these results we have suggested that in contrast to the membrane anchoring of the PBP4 and PBP6b C-terminal a-helices the PBP5 and PBP6 C-terminal a-helices may possess hydrophobicity gradients and penetrate membranes in an oblique orientation. Keywords penicillin-binding protein C-terminal a-helix hydrophobicity gradient membrane. The Escherichia coli low molecular mass penicillin-binding proteins PBPs include PBP4 PBP5
