title: Branching sites and morphological abnormalities behave as ectopic poles in shape-defective Escherichia coli.
abstract: Certain mutants in Escherichia coli lacking multiple penicillin-binding proteins (PBPs) produce misshapen cells containing kinks, bends and branches. These deformed regions exhibit two structural characteristics of normal cell poles: the peptidoglycan is inert to dilution by new synthesis or turnover, and a similarly stable patch of outer membrane caps the sites. To test the premise that these aberrant sites represent biochemically functional but misplaced cell poles, we assessed the intracellular distribution of proteins that localize specifically to bacterial poles. Green fluorescent protein (GFP) hybrids containing polar localization sequences from the Shigella flexneri IcsA protein or from the Vibrio cholerae EpsM protein formed foci at the poles of wild-type E. coli and at the poles and morphological abnormalities in PBP mutants. In addition, secreted wild-type IcsA localized to the outer membrane overlying these aberrant domains. We conclude that the morphologically deformed sites in these mutants represent fully functional poles or pole fragments. The results suggest that prokaryotic morphology is driven, at least in part, by the controlled placement of polar material, and that one or more of the low-molecular-weight PBPs participate in this process. Such mutants may help to unravel how particular proteins are targeted to bacterial poles, thereby creating important biochemical and functional asymmetries.
authors.affiliation: Infectious Disease Division, Massachusetts General Hospital/Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Trine
authors.initials: T
authors.lastname: Nilsen
authors.forename: Anindya S
authors.initials: AS
authors.lastname: Ghosh
authors.forename: Marcia B
authors.initials: MB
authors.lastname: Goldberg
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Young
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006602:Hexosyltransferases / Q000235:genetics*; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D002267:Muramoylpentapeptide Carboxypeptidase / Q000235:genetics*; D009154:Mutation; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan / Q000378:metabolism; D010458:Peptidyl Transferases / Q000235:genetics*; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012763:Shigella flexneri / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C083759:EpsM protein, Vibrio cholerae; D029968:Escherichia coli Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C058483:virG protein, Shigella flexneri; D049452:Green Fluorescent Proteins; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase