View source for 6vhq


==Crystal structure of Bacillus subtilis levansucrase (D86A/E342A) in complex with oligosaccharides==
<StructureSection load='6vhq' size='340' side='right'caption='[[6vhq]], [[Resolution|resolution]] 2.05&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[6vhq]] is a 2 chain structure with sequence from [https://en.wikipedia.org/wiki/Bacillus_subtilis Bacillus subtilis]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=6VHQ OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=6VHQ FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 2.047&#8491;</td></tr>
<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=BR:BROMIDE+ION'>BR</scene>, <scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=FRU:FRUCTOSE'>FRU</scene>, <scene name='pdbligand=PRD_900051:levanbiose'>PRD_900051</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=6vhq FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=6vhq OCA], [https://pdbe.org/6vhq PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=6vhq RCSB], [https://www.ebi.ac.uk/pdbsum/6vhq PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=6vhq ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/SACB_BACSU SACB_BACSU] 
<div style="background-color:#fffaf0;">
== 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<ref>PMID:33303628</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
</div>
<div class="pdbe-citations 6vhq" style="background-color:#fffaf0;"></div>
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Bacillus subtilis]]
[[Category: Large Structures]]
[[Category: Diaz-Vilchis A]]
[[Category: Olvera C]]
[[Category: Raga-Carbajal E]]
[[Category: Rojas-Trejo S]]
[[Category: Rudino-Pinera E]]