title: Differential functionalities of amphiphilic peptide segments of the cell-septation penicillin-binding protein 3 of Escherichia coli.
abstract: The class B M1-V577 penicillin-binding protein (PBP) 3 of Escherichia coli consists of a M1-L39 membrane anchor (bearing a cytosolic tail) that is linked via a G40-S70 intervening peptide to an R71-I236 non-catalytic module (containing the conserved motifs 1-3) itself linked via motif 4 to a D237-V577 catalytic module (containing the conserved motifs 5-7 of the penicilloyl serine transferases superfamily). It has been proposed that during cell septation the peptidoglycan crosslinking activity of the acyl transferase module of PBP3 is regulated by the associated M1-I236 polypeptide itself in interaction with other components of the divisome. The fold adopted by the R71-V577 polypeptide of PBP3 has been modelled by reference to the corresponding R76-S634 polypeptide of the class B Streptococcus pneumoniae PBP2x. Based on these data and the results of site-directed mutagenesis of motifs 1-3 and of peptide segments of high amphiphilicity (identified from hydrophobic moment plots), the M1-I236 polypeptide of PBP3 appears to be precisely designed to work in the way proposed. The membrane anchor and the G40-S70 sequence (containing the G57-Q66 peptide segment) upstream from the non-catalytic module have the information ensuring that PBP3 undergoes proper insertion within the divisome at the cell septation site. Motif 1 and the I74-L82 overlapping peptide segment, motif 2 and the H160-G172 overlapping peptide segment, and the G188-D197 motif 3 are located at or close to the intermodule junction. They contain the information ensuring that PBP3 folds correctly and the acyl transferase catalytic centre adopts the active configuration. The E206-V217 peptide segment is exposed at the surface of the non-catalytic module. It has the information ensuring that PBP3 fulfils its cell septation activity within the fully complemented divisome.
authors.affiliation: Centre d'Ingénierie des Protéines, Université de Liège, Institut de Chimie, B6, Sart Tilman, B-4000 Liège, Belgium. mng.disteche@ulg.ac.be
authors.forename: M
authors.initials: M
authors.lastname: Marrec-Fairley
authors.forename: A
authors.initials: A
authors.lastname: Piette
authors.forename: X
authors.initials: X
authors.lastname: Gallet
authors.forename: R
authors.initials: R
authors.lastname: Brasseur
authors.forename: H
authors.initials: H
authors.lastname: Hara
authors.forename: C
authors.initials: C
authors.lastname: Fraipont
authors.forename: J M
authors.initials: JM
authors.lastname: Ghuysen
authors.forename: M
authors.initials: M
authors.lastname: Nguyen-Distèche
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001426:Bacterial Proteins; D001665:Binding Sites; D002352:Carrier Proteins; D004926:Escherichia coli / Q000737:chemistry*; D029968:Escherichia coli Proteins; D006602:Hexosyltransferases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002267:Muramoylpentapeptide Carboxypeptidase; D046915:Penicillin-Binding Proteins; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D046928:Peptidoglycan Glycosyltransferase; D010458:Peptidyl Transferases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C478704:FtsI protein, E coli; D009097:Multienzyme Complexes; D046915:Penicillin-Binding Proteins; D010455:Peptides; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D046928:Peptidoglycan Glycosyltransferase; D002267:Muramoylpentapeptide Carboxypeptidase