Spratt, B. G. Distinct penicillin binding proteins involved in the division, elongation, and shape of Escherichia coli K12. Proc. Natl Acad. Sci. USA 72, 2999-3003

Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 09/1975; 72(8):2999-3003. DOI: 10.1073/pnas.72.8.2999
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The varied effects of beta-lactam antibiotics on cell division, cell elongation, and cell shape in E. coli are shown to be due to the presence of three essential penicillin binding proteins with distinct roles in these three processes. (A) Cell shape: beta-Lactams that specifically result in the production of ovoid cells bind to penicillin binding protein 2 (molecular weight 66,000). A mutant has been isolated that fails to bind beta-lactams to protein 2, and that grows as round cells. (B) Cell division: beta-Lactams that specifically inhibit cell division bind preferentially to penicillin binding protein 3 (molecular weight 60,000). A temperature-sensitive cell division mutant has been shown to have a thermolabile protein 3. (C) Cell elongation: One beta-lactam that preferentially inhibits cell elongation and causes cell lysis binds preferentially to binding protein 1 (molecular weight 91,000). Evidence is presented that penicillin bulge formation is due to the inhibition of proteins 2 and 3 in the absence of inhibition of protein 1.

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Available from: Brian Spratt, Jul 16, 2015
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    • "Transpeptidation generates cross-links between PG peptide side-chains, typically by linking the D-alanine in the fourth position of a donor pentapeptide (often L-Ala→D-Glu→meso- DAP→D-Ala→D-Ala in Gram-negative bacteria) to the third position meso-DAP of an acceptor peptide strand (Höltje, 1998). In Escherichia coli, the activities of HMW PBPs have been fairly well defined, and two of the five (PBP2 and PBP3) are essential for cell elongation and cell division (Spratt, 1975). The enzymes with the highest synthetic activity – PBP1A and PBP1B – are individually dispensable, but cannot be disrupted simultaneously (Yousif et al., 1985; Dörr et al., 2014). "
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    ABSTRACT: The biological roles of low molecular weight penicillin-binding proteins (LMW PBP) have been difficult to discern in Gram-negative organisms. In E. coli, mutants lacking these proteins often have no phenotype, and cells lacking all 7 LMW PBPs remain viable. In contrast, we report here that Vibrio cholerae lacking DacA-1, a PBP5 homolog, displays slow growth, aberrant morphology, and altered peptidoglycan (PG) homeostasis in LB medium, as well as a profound plating defect. DacA-1 alone among V. cholerae's LMW PBPs is critical for bacterial growth; mutants lacking the related protein DacA-2 and/or homologs of PBP4 or PBP7 displayed normal growth and morphology. Remarkably, the growth and morphology of the dacA-1 mutant were unimpaired in LB media containing reduced concentrations of NaCl (100 mM or less), and also within suckling mice, a model host for the study of cholera pathogenesis. PG from the dacA-1 mutant contained elevated pentapeptide levels in standard and low salt media, and comparative analyses suggest that DacA-1 is V. cholerae's principal DD-carboxypeptidase. The basis for the dacA-1 mutant's halosensitivity is unknown; nonetheless, the mutant's survival in biochemically uncharacterized environments (such as the suckling mouse intestine) can be used as a reporter of low Na+ content.
    Environmental Microbiology 01/2015; 17(2). DOI:10.1111/1462-2920.12779 · 6.20 Impact Factor
    • "sahare@gmail . com Spratt ( 1975 - 77 "
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    • "Filamentation, in which cells continue to elongate but do not divide, is often observed in bacteria exposed to various stresses. Filamentation of E. coli in response to beta-lactams [12] and fluoroquinolones [12], [13] is well known. The effect of fluoroquinolones has been shown to be dose dependent with greater filamentation at the minimal inhibitory concentration (MIC) of ciprofloxacin compared to 100 times the MIC [13]. "
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    ABSTRACT: It was recently proposed that for bactericidal antibiotics a common killing mechanism contributes to lethality involving indirect stimulation of hydroxyl radical (OH•) formation. Flow cytometric detection of OH• by hydroxyphenyl fluorescein (HPF) probe oxidation was used to support this hypothesis. Here we show that increased HPF signals in antibiotics-exposed bacterial cells are explained by fluorescence associated with increased cell size, and do not reflect reactive oxygen species (ROS) concentration. Independently of antibiotics, increased fluorescence was seen for elongated cells expressing the oxidative insensitive green fluorescent protein (GFP). Although our data question the role of ROS in lethality of antibiotics other research approaches point to important interplays between basic bacterial metabolism and antibiotic susceptibility. To underpin such relationships, methods for detecting bacterial metabolites at a cellular level are needed.
    PLoS ONE 03/2014; 9(3):e92231. DOI:10.1371/journal.pone.0092231 · 3.23 Impact Factor
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