PMID:16618494

Citation	Powell, AJ, Liu, ZJ, Nicholas, RA and Davies, C (2006) Crystal structures of the lytic transglycosylase MltA from N.gonorrhoeae and E.coli: insights into interdomain movements and substrate binding. J. Mol. Biol. 359:122-36
Abstract	MltA is a lytic transglycosylase of Gram-negative bacteria that cleaves the beta-1,4 glycosidic linkages between N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) in peptidoglycan. We have determined the crystal structures of MltA from Neisseria gonorrhoeae and Escherichia coli (NgMltA and EcMltA), which have only 21.5% sequence identity. Both proteins have two main domains separated by a deep groove. Domain 1 shows structural similarity with the so-called double-psi barrel family of proteins. Comparison of the two structures reveals substantial differences in the relative positions of domains 1 and 2 such that the active site groove in NgMltA is much wider and appears more able to accommodate peptidoglycan substrate than EcMltA, suggesting that domain closure occurs after substrate binding. Docking of a peptidoglycan molecule into the structure of NgMltA reveals a number of conserved residues that are likely involved in substrate binding, including a potential binding pocket for the peptidyl moieties. This structure supports the assignment of Asp405 as the acid catalyst responsible for cleavage of the glycosidic bond. In EcMltA, the equivalent residue is Asp328, which has been identified previously. The structures also suggest a catalytic role for Asp393 (Asp317 in EcMltA) in activating the C6 hydroxyl group during formation of the 1,6-anhydro linkage. Finally, in comparison to EcMltA, NgMltA contains a unique third domain that is an insertion within domain 2. The domain is beta in structure and may mediate protein-protein interactions that are specific to peptidoglycan metabolism in N.gonorrhoeae.
Links	PubMed Online version:10.1016/j.jmb.2006.03.023
Keywords	Amino Acid Sequence; Bacterial Proteins/chemistry; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Binding Sites; Carbohydrates/chemistry; Crystallography, X-Ray; Escherichia coli/enzymology; Glycosyltransferases/chemistry; Glycosyltransferases/genetics; Glycosyltransferases/metabolism; Models, Molecular; Molecular Sequence Data; Molecular Structure; Neisseria gonorrhoeae/enzymology; Protein Binding; Protein Folding; Protein Structure, Secondary; Protein Structure, Tertiary; Sequence Alignment
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
9CAUD:A0A0K2CZX2		GO:2000966: peptidoglycan turnover	ECO:0000250:	UniProtKB:A0A023Z1P7 UniProtKB:A0A0G4BQJ3	P		MltA is a lytic transglycosylase of Gram-negative bacteria that cleaves the beta-1,4 glycosidic linkages between N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) in peptidoglycan. Since these sites have determined the crystal structures of MltA from Neisseria gonorrhoeae and Escherichia coli (NgMltA and EcMltA), which have only 21.5% sequence identity but have 2 main domains separated by a deep grove pointing that they are both MltA proteins, we can conclude that this protein in Bacillus phage TsarBomba is also a MltA protein with the same protein function.	complete CACAO 11432
NEIME:A0A0G4BQJ3		GO:2000966: regulation of cell wall polysaccharide catabolic process	ISS: Inferred from Sequence Similarity: UniProtKB:A0A023Z1P7	P	MltA is a lytic transglycosylase of Gram-negative bacteria that cleaves the beta-1,4 glycosidic linkages between N-acetylmuramic acid (MurNAc) and N-acetylglucosamine (GlcNAc) in peptidoglycan. We have determined the crystal structures of MltA from Neisseria gonorrhoeae and Escherichia coli (NgMltA and EcMltA), which have only 21.5% sequence identity but have 2 main domains separated by a deep grove pointing that they are both MltA proteins.	complete CACAO 11435

References

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