Protein Domain : Lytic transglycosylase MltB IPR011757

Type	Family
Description	This family consists of lytic murein transglycosylases (murein hydrolases) related to MltB ( ), which is a 38kDa membrane-bound lipoprotein in Escherichia coli. The N-terminal region of this protein contains a lipoprotein-processing site which is conserved in about half the members of this family. Proteolytic cleavage of MltB produces a fully-active, soluble form of this enzyme known as Slt35 (for soluble lytic transglycosylase). This enzyme catalyzes the cleavage of the glycosidic bonds between N-acetylmuramic acid and N-acetylglucosamine residues in peptidoglycan. Its physiological role is unknown as deletion of the gene shows no obvious phenotype [ ], though it has been suggested to play a role in recycling of muropeptides during cell elongation and/or cell division.The Slt35 enzyme is a monomer with an ellipsoid shape and is composed of three distinct domains known as the alpha, beta and core domains [ , ]. The alpha domain contains mainly α-helices, while the beta domain consists of a five-stranded antiparallel β-sheet flanked by a short α-helix. The core domain is sandwiched between the alpha and beta domains and its fold is similar to that of lysozyme, but contains a single metal ion binding site in a helix-loop-helix module that is similar to the eukaryotic EF-hand calcium-binding fold, though in this case the loop is slightly longer than usual. Binding of Ca(2+) to this EF hand motif has been shown to be important for thermal stability of the protein []. The substrate binding sites are found in the cleft formed by the core domain of the enzyme [].Members of this family do not contain the putative peptidoglycan binding domain described by , which is associated with several other classes of bacterial cell wall lytic enzymes.
Short Name	Lytic_transglycosylase_MltB