6t18

ASR Alternansucrase in complex with oligoalternan

spinqualitylabelsall models 6t18, resolution 3.15Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6t18 is a 2 chain structure with sequence from Leuconostoc mesenteroides. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 3.15Å Ligands: CA, GLC Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function Q9RE05_LEUME Publication Abstract from PubMed Microbial alpha-glucans produced by glycoside hydrolase family 70 (GH70) glucansucrases are gaining importance because of the mild conditions for their synthesis from sucrose, their biodegradability, and their current and anticipated applications that largely depend on their molar mass. Focusing on the alternansucrase (ASR) from Leuconostoc citreum NRRL B-1355, a well-known glucansucrase catalyzing the synthesis of both high-molar mass (HMM) and low-molar mass alternans, we searched for structural traits in ASR that could be involved in the control of alternan elongation. The resolution of five crystal structures of a truncated ASR version (ASRDelta2) in complex with different gluco-oligosaccharides pinpointed key residues in binding sites located in the A and V domains of ASR. Biochemical characterization of three single mutants and three double mutants, targeting the sugar-binding pockets identified in domain V, revealed an involvement of this domain in alternan binding and elongation. More strikingly, we found an oligosaccharide-binding site at the surface of domain A, distant from the catalytic site and not previously identified in other glucansucrases. We named this site surface binding site A1 (SBS-A1). Among the residues lining the SBS-A1 site, two (Gln-700 and Tyr-717) promoted alternan elongation. Their substitution to alanine decreased HMM alternan yield by a third, without significantly impacting enzyme stability or specificity. We propose that the SBS-A1 site is unique to alternansucrase and appears to be designed to bind alternating structures, acting as a mediator between the catalytic site and the sugar-binding pockets of domain V and contributing to a processive elongation of alternan chains. A specific oligosaccharide-binding site in alternansucrase catalytic domain mediates alternan elongation.,Molina M, Moulis C, Monties N, Guieysse D, Morel S, Cioci G, Remaud-Simeon M J Biol Chem. 2020 May 14. pii: RA120.013028. doi: 10.1074/jbc.RA120.013028. PMID:32409580 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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