Cofactor bypass variants reveal a conformational control mechanism governing cell wall polymerase activity

Monica Markovski, Jessica L. Bohrhunter, Tania Lupoli, Tsuyoshi Uehara, Suzanne Walker, Daniel E. Kahne, Thomas G. Bernhardt

Research output: Contribution to journalArticle

Abstract

To fortify their cytoplasmic membrane and protect it from osmotic rupture, most bacteria surround themselves with a peptidoglycan (PG) exoskeleton synthesized by the penicillin-binding proteins (PBPs). As their name implies, these proteins are the targets of penicillin and related antibiotics. We and others have shown that the PG synthases PBP1b and PBP1a of Escherichia coli require the outer membrane lipoproteins LpoA and LpoB, respectively, for their in vivo function. Although it has been demonstrated that LpoB activates the PG polymerization activity of PBP1b in vitro, the mechanism of activation and its physiological relevance have remained unclear. We therefore selected for variants of PBP1b (PBP1b∗) that bypass the LpoB requirement for in vivo function, reasoning that they would shed light on LpoB function and its activation mechanism. Several of these PBP1b variants were isolated and displayed elevated polymerization activity in vitro, indicating that the activation of glycan polymer growth is indeed one of the relevant functions of LpoB in vivo. Moreover, the location of amino acid substitutions causing the bypass phenotype on the PBP1b structure support a model in which polymerization activation proceeds via the induction of a conformational change in PBP1b initiated by LpoB binding to its UB2H domain, followed by its transmission to the glycosyl transferase active site. Finally, phenotypic analysis of strains carrying a PBP1b∗variant revealed that the PBP1bLpoB complex is most likely not providing an important physical link between the inner and outer membranes at the division site, as has been previously proposed.

Original languageEnglish (US)
Pages (from-to)4788-4793
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number17
DOIs
StatePublished - Apr 26 2016

Fingerprint

Peptidoglycan
Polymerization
Cell Wall
Penicillin-Binding Proteins
Membranes
Amino Acid Substitution
Transferases
Penicillins
Lipoproteins
Names
Polysaccharides
Rupture
Catalytic Domain
Polymers
Cell Membrane
Escherichia coli
Bacteria
Phenotype
Growth
Proteins

ASJC Scopus subject areas

  • General

Cite this

Cofactor bypass variants reveal a conformational control mechanism governing cell wall polymerase activity. / Markovski, Monica; Bohrhunter, Jessica L.; Lupoli, Tania; Uehara, Tsuyoshi; Walker, Suzanne; Kahne, Daniel E.; Bernhardt, Thomas G.

In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 113, No. 17, 26.04.2016, p. 4788-4793.

Research output: Contribution to journalArticle

Markovski, Monica ; Bohrhunter, Jessica L. ; Lupoli, Tania ; Uehara, Tsuyoshi ; Walker, Suzanne ; Kahne, Daniel E. ; Bernhardt, Thomas G. / Cofactor bypass variants reveal a conformational control mechanism governing cell wall polymerase activity. In: Proceedings of the National Academy of Sciences of the United States of America. 2016 ; Vol. 113, No. 17. pp. 4788-4793.
@article{bfebfd7269c5473a9f894453b23c6974,
title = "Cofactor bypass variants reveal a conformational control mechanism governing cell wall polymerase activity",
abstract = "To fortify their cytoplasmic membrane and protect it from osmotic rupture, most bacteria surround themselves with a peptidoglycan (PG) exoskeleton synthesized by the penicillin-binding proteins (PBPs). As their name implies, these proteins are the targets of penicillin and related antibiotics. We and others have shown that the PG synthases PBP1b and PBP1a of Escherichia coli require the outer membrane lipoproteins LpoA and LpoB, respectively, for their in vivo function. Although it has been demonstrated that LpoB activates the PG polymerization activity of PBP1b in vitro, the mechanism of activation and its physiological relevance have remained unclear. We therefore selected for variants of PBP1b (PBP1b∗) that bypass the LpoB requirement for in vivo function, reasoning that they would shed light on LpoB function and its activation mechanism. Several of these PBP1b variants were isolated and displayed elevated polymerization activity in vitro, indicating that the activation of glycan polymer growth is indeed one of the relevant functions of LpoB in vivo. Moreover, the location of amino acid substitutions causing the bypass phenotype on the PBP1b structure support a model in which polymerization activation proceeds via the induction of a conformational change in PBP1b initiated by LpoB binding to its UB2H domain, followed by its transmission to the glycosyl transferase active site. Finally, phenotypic analysis of strains carrying a PBP1b∗variant revealed that the PBP1bLpoB complex is most likely not providing an important physical link between the inner and outer membranes at the division site, as has been previously proposed.",
author = "Monica Markovski and Bohrhunter, {Jessica L.} and Tania Lupoli and Tsuyoshi Uehara and Suzanne Walker and Kahne, {Daniel E.} and Bernhardt, {Thomas G.}",
year = "2016",
month = "4",
day = "26",
doi = "10.1073/pnas.1524538113",
language = "English (US)",
volume = "113",
pages = "4788--4793",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
issn = "0027-8424",
number = "17",

}

TY - JOUR

T1 - Cofactor bypass variants reveal a conformational control mechanism governing cell wall polymerase activity

AU - Markovski, Monica

AU - Bohrhunter, Jessica L.

AU - Lupoli, Tania

AU - Uehara, Tsuyoshi

AU - Walker, Suzanne

AU - Kahne, Daniel E.

AU - Bernhardt, Thomas G.

PY - 2016/4/26

Y1 - 2016/4/26

N2 - To fortify their cytoplasmic membrane and protect it from osmotic rupture, most bacteria surround themselves with a peptidoglycan (PG) exoskeleton synthesized by the penicillin-binding proteins (PBPs). As their name implies, these proteins are the targets of penicillin and related antibiotics. We and others have shown that the PG synthases PBP1b and PBP1a of Escherichia coli require the outer membrane lipoproteins LpoA and LpoB, respectively, for their in vivo function. Although it has been demonstrated that LpoB activates the PG polymerization activity of PBP1b in vitro, the mechanism of activation and its physiological relevance have remained unclear. We therefore selected for variants of PBP1b (PBP1b∗) that bypass the LpoB requirement for in vivo function, reasoning that they would shed light on LpoB function and its activation mechanism. Several of these PBP1b variants were isolated and displayed elevated polymerization activity in vitro, indicating that the activation of glycan polymer growth is indeed one of the relevant functions of LpoB in vivo. Moreover, the location of amino acid substitutions causing the bypass phenotype on the PBP1b structure support a model in which polymerization activation proceeds via the induction of a conformational change in PBP1b initiated by LpoB binding to its UB2H domain, followed by its transmission to the glycosyl transferase active site. Finally, phenotypic analysis of strains carrying a PBP1b∗variant revealed that the PBP1bLpoB complex is most likely not providing an important physical link between the inner and outer membranes at the division site, as has been previously proposed.

AB - To fortify their cytoplasmic membrane and protect it from osmotic rupture, most bacteria surround themselves with a peptidoglycan (PG) exoskeleton synthesized by the penicillin-binding proteins (PBPs). As their name implies, these proteins are the targets of penicillin and related antibiotics. We and others have shown that the PG synthases PBP1b and PBP1a of Escherichia coli require the outer membrane lipoproteins LpoA and LpoB, respectively, for their in vivo function. Although it has been demonstrated that LpoB activates the PG polymerization activity of PBP1b in vitro, the mechanism of activation and its physiological relevance have remained unclear. We therefore selected for variants of PBP1b (PBP1b∗) that bypass the LpoB requirement for in vivo function, reasoning that they would shed light on LpoB function and its activation mechanism. Several of these PBP1b variants were isolated and displayed elevated polymerization activity in vitro, indicating that the activation of glycan polymer growth is indeed one of the relevant functions of LpoB in vivo. Moreover, the location of amino acid substitutions causing the bypass phenotype on the PBP1b structure support a model in which polymerization activation proceeds via the induction of a conformational change in PBP1b initiated by LpoB binding to its UB2H domain, followed by its transmission to the glycosyl transferase active site. Finally, phenotypic analysis of strains carrying a PBP1b∗variant revealed that the PBP1bLpoB complex is most likely not providing an important physical link between the inner and outer membranes at the division site, as has been previously proposed.

UR - http://www.scopus.com/inward/record.url?scp=84964790243&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84964790243&partnerID=8YFLogxK

U2 - 10.1073/pnas.1524538113

DO - 10.1073/pnas.1524538113

M3 - Article

C2 - 27071112

AN - SCOPUS:84964790243

VL - 113

SP - 4788

EP - 4793

JO - Proceedings of the National Academy of Sciences of the United States of America

JF - Proceedings of the National Academy of Sciences of the United States of America

SN - 0027-8424

IS - 17

ER -