Loss of a functionally and structurally distinct LD-transpeptidase, LdtMt5, compromises cell wall integrity in mycobacterium tuberculosis

Leighanne A Brammer Basta, Anita Ghosh, Ying Pan, Jean Jakoncic, Evan P. Lloyd, Craig A. Townsend, Gyanu Lamichhane, Mario Antonio Bianchet

Research output: Contribution to journalArticle

Abstract

The final step of peptidoglycan (PG) biosynthesis in bacteria involves cross-linking of peptide side chains. This step in Mycobacterium tuberculosis is catalyzed by LD- and DD-transpeptidases that generate 3→3 and 4→3 transpeptide linkages, respectively. M. tuberculosis PG is predominantly 3→3 cross-linked, and LdtMt2 is the dominant LD-transpeptidase. There are four additional sequence paralogs of LdtMt2 encoded by the genome of this pathogen, and the reason for this apparent redundancy is unknown. Here, we studied one of the paralogs, LdtMt5 , and found it to be structurally and functionally distinct. The structures of apo-LdtMt5 and its meropenem adduct presented here demonstrate that, despite overall architectural similarity to LdtMt2 , the LdtMt5 active site has marked differences. The presence of a structurally divergent catalytic site and a proline-rich C-terminal subdomain suggest that this protein may have a distinct role in PG metabolism, perhaps involving other cell wall-anchored proteins. Furthermore, M. tuberculosis lacking a functional copy of LdtMt5 displayed aberrant growth and was more susceptible to killing by crystal violet, osmotic shock, and select carbapenem antibiotics. Therefore, we conclude that LdtMt5 is not a functionally redundant LD-transpeptidase, but rather it serves a unique and important role in maintaining the integrity of the M. tuberculosis cell wall.

Original languageEnglish (US)
Pages (from-to)25670-25685
Number of pages16
JournalJournal of Biological Chemistry
Volume290
Issue number42
DOIs
StatePublished - Oct 16 2015

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Peptidyl Transferases
Peptidoglycan
Mycobacterium tuberculosis
Cell Wall
meropenem
Cells
Gentian Violet
Catalytic Domain
Carbapenems
Biosynthesis
Pathogens
Proline
Metabolism
Redundancy
Osmotic Pressure
Bacteria
Proteins
Genes
Peptides
Genome

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

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Loss of a functionally and structurally distinct LD-transpeptidase, LdtMt5, compromises cell wall integrity in mycobacterium tuberculosis. / Basta, Leighanne A Brammer; Ghosh, Anita; Pan, Ying; Jakoncic, Jean; Lloyd, Evan P.; Townsend, Craig A.; Lamichhane, Gyanu; Bianchet, Mario Antonio.

In: Journal of Biological Chemistry, Vol. 290, No. 42, 16.10.2015, p. 25670-25685.

Research output: Contribution to journalArticle

Basta, Leighanne A Brammer ; Ghosh, Anita ; Pan, Ying ; Jakoncic, Jean ; Lloyd, Evan P. ; Townsend, Craig A. ; Lamichhane, Gyanu ; Bianchet, Mario Antonio. / Loss of a functionally and structurally distinct LD-transpeptidase, LdtMt5, compromises cell wall integrity in mycobacterium tuberculosis. In: Journal of Biological Chemistry. 2015 ; Vol. 290, No. 42. pp. 25670-25685.
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abstract = "The final step of peptidoglycan (PG) biosynthesis in bacteria involves cross-linking of peptide side chains. This step in Mycobacterium tuberculosis is catalyzed by LD- and DD-transpeptidases that generate 3→3 and 4→3 transpeptide linkages, respectively. M. tuberculosis PG is predominantly 3→3 cross-linked, and LdtMt2 is the dominant LD-transpeptidase. There are four additional sequence paralogs of LdtMt2 encoded by the genome of this pathogen, and the reason for this apparent redundancy is unknown. Here, we studied one of the paralogs, LdtMt5 , and found it to be structurally and functionally distinct. The structures of apo-LdtMt5 and its meropenem adduct presented here demonstrate that, despite overall architectural similarity to LdtMt2 , the LdtMt5 active site has marked differences. The presence of a structurally divergent catalytic site and a proline-rich C-terminal subdomain suggest that this protein may have a distinct role in PG metabolism, perhaps involving other cell wall-anchored proteins. Furthermore, M. tuberculosis lacking a functional copy of LdtMt5 displayed aberrant growth and was more susceptible to killing by crystal violet, osmotic shock, and select carbapenem antibiotics. Therefore, we conclude that LdtMt5 is not a functionally redundant LD-transpeptidase, but rather it serves a unique and important role in maintaining the integrity of the M. tuberculosis cell wall.",
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AU - Jakoncic, Jean

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