Family

UDP-N-acetylmuramate-alanine ligase (IPR005758)

Short name: UDP-N-AcMur_Ala_ligase

Family relationships

None.

Description

The bacterial cell wall provides strength and rigidity to counteract internal osmotic pressure, and protection against the environment. The peptidoglycan layer gives the cell wall its strength, and helps maintain the overall shape of the cell. The basic peptidoglycan structure of both Gram-positive and Gram-negative bacteria is comprised of a sheet of glycan chains connected by short cross-linking polypeptides. Biosynthesis of peptidoglycan is a multi-step (11-12 steps) process comprising three main stages:

  • (1) formation of UDP-N-acetylmuramic acid (UDPMurNAc) from N-acetylglucosamine (GlcNAc).
  • (2) addition of a short polypeptide chain to the UDPMurNAc.
  • (3) addition of a second GlcNAc to the disaccharide-pentapeptide building block and transport of this unit through the cytoplasmic membrane and incorporation into the growing peptidoglycan layer.

Stage two involves four key Mur ligase enzymes: MurC (EC:6.3.2.8) [PMID: 17139082], MurD (EC:6.3.2.9) [PMID: 17427948], MurE (EC:6.3.2.13) [PMID: 16595662] and MurF (EC:6.3.2.10) [PMID: 16322581]. These four Mur ligases are responsible for the successive additions of L-alanine, D-glutamate, meso-diaminopimelate or L-lysine, and D-alanyl-D-alanine to UDP-N-acetylmuramic acid. All four Mur ligases are topologically similar to one another, even though they display low sequence identity. They are each composed of three domains: an N-terminal Rossmann-fold domain responsible for binding the UDPMurNAc substrate; a central domain (similar to ATP-binding domains of several ATPases and GTPases); and a C-terminal domain (similar to dihydrofolate reductase fold) that appears to be associated with binding the incoming amino acid. The conserved sequence motifs found in the four Mur enzymes also map to other members of the Mur ligase family, including folylpolyglutamate synthetase, cyanophycin synthetase and the capB enzyme from Bacillales [PMID: 16934839].

This entry represents UDP-N-acetylmuramate-alanine ligase (MurC). MurC is an essential, cytoplasmic peptidoglycan biosynthetic enzyme, catalyzes the ATP-dependent ligation of L-alanine (Ala) and UDP-N-acetylmuramic acid (UNAM) to form UDP-N-acetylmuramyl-L-alanine (UNAM-Ala). The enzyme is a nonribosomal peptide ligase which utilises ATP to form an amide bond between L-alanine and UNAM.1 Mechanistic studies on the Escherichia coli MurC enzyme using oxygen isotope analyses demonstrated that the enzyme-catalyzed reaction proceeds through an acyl phosphate UNAM intermediate prior to L-alanine addition.

GO terms

Biological Process

GO:0051301 cell division
GO:0008360 regulation of cell shape

Molecular Function

GO:0005524 ATP binding
GO:0008763 UDP-N-acetylmuramate-L-alanine ligase activity

Cellular Component

GO:0005737 cytoplasm

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
TIGRFAMs
HAMAP