1qsa
From Proteopedia
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CRYSTAL STRUCTURE OF THE 70 KDA SOLUBLE LYTIC TRANSGLYCOSYLASE SLT70 FROM ESCHERICHIA COLI AT 1.65 ANGSTROMS RESOLUTION
Overview
The 70 kDa soluble lytic transglycosylase (Slt70) from Escherichia coli is, an exo-muramidase, that catalyses the cleavage of the glycosidic bonds, between N -acetylmuramic acid and N -acetylglucosamine residues in, peptidoglycan, the main structural component of the bacterial cell wall., This cleavage is accompanied by the formation of a 1,6-anhydro bond, between the C1 and O6 atoms in the N -acetylmuramic acid residue, (anhMurNAc). Crystallographic studies at medium resolution revealed that, Slt70 is a multi-domain protein consisting of a large ring-shaped, alpha-superhelix with on top a catalytic domain, which resembles the fold, of goose-type lysozyme. Here we report the crystal structures of native, Slt70 and of its complex with a 1,6-anhydromuropeptide solved at nominal, resolutions of 1.65 A and 1.90 A, respectively. The high resolution native, structure reveals the details on the hydrogen bonds, electrostatic and, hydrophobic interactions that stabilise the catalytic domain and the, alpha-superhelix. The building-block of the alpha-superhelix is an, "up-down-up-down" four-alpha-helix bundle involving both parallel and, antiparallel helix pairs. Stabilisation of the fold is provided through an, extensive packing of apolar atoms, mostly from leucine and alanine, residues. It lacks, however, an internal consensus sequence that, characterises other super-secondary helical folds like the beta-helix in, pectate lyase or the (beta-alpha)-helix in the ribonuclease inhibitor. The, 1, 6-anhydromuropeptide product binds in a shallow groove adjacent to the, peptidoglycan-binding groove of the catalytic domain. The groove is formed, by conserved residues at the interface of the catalytic domain and the, alpha-superhelix. The structure of the Slt70-1, 6-anhydromuropeptide, complex confirms the presence of a specific binding-site for the peptide, moieties of the peptidoglycan and it substantiates the notion that Slt70, starts the cleavage reaction at the anhMurNAc end of the peptidoglycan.
About this Structure
1QSA is a Single protein structure of sequence from Escherichia coli with SO4, ACT and GOL as ligands. Full crystallographic information is available from OCA.
Reference
High resolution crystal structures of the Escherichia coli lytic transglycosylase Slt70 and its complex with a peptidoglycan fragment., van Asselt EJ, Thunnissen AM, Dijkstra BW, J Mol Biol. 1999 Aug 27;291(4):877-98. PMID:10452894
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