6vhq

Crystal structure of Bacillus subtilis levansucrase (D86A/E342A) in complex with oligosaccharides

spinqualitylabelsall models 6vhq, resolution 2.05Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 6vhq is a 2 chain structure with sequence from Bacillus subtilis. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.047Å Ligands: BR, CA, FRU, PRD_900051 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function SACB_BACSU Publication Abstract from PubMed Levansucrases (LSs) synthesize levan, a beta2-6-linked fructose polymer, by successively transferring the fructosyl moiety from sucrose to a growing acceptor molecule. Elucidation of the levan polymerization mechanism is important for using LSs in the production of size-defined products for application in the food and pharmaceutical industries. For a deeper understanding of the levan synthesis reaction, we determined the crystallographic structure of Bacillus subtilis LS (SacB) in complex with a levan-type fructooligosaccharide and utilized site-directed mutagenesis to identify residues involved in substrate binding. The presence of a levanhexaose molecule in the central catalytic cavity allowed us to identify five substrate-binding subsites (-1, +1, +2, +3, and +4). Mutants affecting residues belonging to the identified acceptor subsites showed similar substrate affinity (Km) values to the wildtype (WT) Km value but had a lower turnover number and transfructosylation/hydrolysis ratio. Of importance, compared with the WT, the variants progressively yielded smaller-sized low-molecular-weight levans, as the affected subsites that were closer to the catalytic site, but without affecting their ability to synthesized high-molecular-weight levans. Furthermore, an additional oligosaccharide-binding site 20 A away from the catalytic pocket was identified, and its potential participation in the elongation mechanism is discussed. Our results clarify, for the first time, the interaction of the enzyme with an acceptor/product oligosaccharide and elucidate the molecular basis of the nonprocessive levan elongation mechanism of LSs. The molecular basis of the nonprocessive elongation mechanism in levansucrases.,Raga-Carbajal E, Diaz-Vilchis A, Rojas-Trejo SP, Rudino-Pinera E, Olvera C J Biol Chem. 2021 Jan-Jun;296:100178. doi: 10.1074/jbc.RA120.015853. Epub 2020, Dec 17. PMID:33303628 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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