title: Alpha-helical conformation in the C-terminal anchoring domains of E. coli penicillin-binding proteins 4, 5 and 6.
abstract: The E. coli low molecular mass penicillin-binding proteins (PBP's) are penicillin sensitive, enzymes involved in the terminal stages of peptidoglycan biosynthesesis. These PBP's are believed to anchor to the periplasmic face of the inner membrane via C-terminal amphiphilic alpha-helices but to date the only support for this hypothesis has been obtained from theoretical analysis. In this paper, the conformational behaviour of synthetic peptides corresponding to these C-terminal anchoring domains was studied as a function of solvent, pH, sodium dodecyl sulphate micelles and phospholipid (DOPC, DOPG) vesicles using circular dichroism (CD) spectroscopy. The CD data showed that in 2,2,2-trifluoroethanol or sodium dodecylsulphate, all three peptides have the capacity to form an alpha-helical conformation but in aqueous solution or in the presence of phospholipid vesicles only those peptides corresponding to the PBP5 and PBP6 C-termini were observed to do so. A pH dependent loss of alpha-helical conformation in the peptide corresponding to the PBP5 C-terminus was found to correlate with the susceptibility of PBP5 to membrane extraction. This correlation would agree with the hypothesis that an alpha-helical conformation is required for membrane interaction of the PBP5 C-terminal region.
authors.affiliation: The EPSRC and ULIRS Chiroptical Laboratory, London, UK.
authors.forename: G
authors.initials: G
authors.lastname: Siligardi
authors.forename: F
authors.initials: F
authors.lastname: Harris
authors.forename: D A
authors.initials: DA
authors.lastname: Phoenix
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000737:chemistry*; D002942:Circular Dichroism; D004926:Escherichia coli; D006602:Hexosyltransferases; D008081:Liposomes; D008969:Molecular Sequence Data; D002267:Muramoylpentapeptide Carboxypeptidase / Q000737:chemistry*; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry; D010458:Peptidyl Transferases; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D017433:Protein Structure, Secondary
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D008081:Liposomes; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D010446:Peptide Fragments; D010455:Peptides; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; C051388:1,2-dioleoyl-sn-glycero-3-phosphoglycerol; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase; C017251:1,2-oleoylphosphatidylcholine