Primary Citation of Related Structures: 2PI8, 2PIC, 2PJJ
PubMed Abstract:
Crystal structures of an inactive mutant (D308A) of the lytic transglycosylase MltA from Escherichia coli have been determined in two different apo-forms, as well as in complex with the substrate analogue chitohexaose. The chitohexaose binds with all six saccharide residues in the active site groove, with an intact glycosidic bond at the bond cleavage center ...
Crystal structures of an inactive mutant (D308A) of the lytic transglycosylase MltA from Escherichia coli have been determined in two different apo-forms, as well as in complex with the substrate analogue chitohexaose. The chitohexaose binds with all six saccharide residues in the active site groove, with an intact glycosidic bond at the bond cleavage center. Its binding induces a large reorientation of the two structural domains in MltA, narrowing the active site groove and allowing tight interactions of the oligosaccharide with residues from both domains. The structures identify residues in MltA with key roles in the binding and recognition of peptidoglycan and confirm that Asp-308 is the single catalytic residue, acting as a general acid/base. Moreover, the structures suggest that catalysis involves a high energy conformation of the scissile glycosidic linkage and that the putative oxocarbenium ion intermediate is stabilized by the dipole moment of a nearby alpha-helix.
Related Citations:
Escherichia coli MltA: MAD phasing and refinement of a tetartohedrally twinned protein crystal structure Barends, T.R.M., de Jong, R.M., van Straaten, K.E., Thunnissen, A.M.W.H., Dijkstra, B.W. (2005) Acta Crystallogr D Biol Crystallogr 61: 613
Crystal structure of MltA from Escherichia coli reveals a unique lytic transglycosylase fold van Straaten, K.E., Dijkstra, B.W., Vollmer, W., Thunnissen, A.M.W.H. (2005) J Mol Biol 352: 1068
Purification, crystallization and preliminary X-ray analysis of the lytic transglycosylase MltA from Escherichia coli van Straaten, K.E., Dijkstra, B.W., Thunnissen, A.M.W.H. (2004) Acta Crystallogr D Biol Crystallogr 60: 758
Organizational Affiliation:
Laboratory of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
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