1pt2: Difference between revisions

[[Image:1pt2.gif|left|200px]]<br /><applet load="1pt2" size="350" color="white" frame="true" align="right" spinBox="true"  

Many bacteria and about 40,000 plant species form primary carbohydrate reserves based on fructan; these polymers of beta-D-fructofuranose are thought to confer tolerance to drought and frost in plants. Microbial fructan, the beta(2,6)-linked levan, is synthesized directly from sucrose by levansucrase, which is able to catalyze both sucrose hydrolysis and levan polymerization. The crystal structure of Bacillus subtilis levansucrase, determined to a resolution of 1.5 A, shows a rare five-fold beta-propeller topology with a deep, negatively charged central pocket. Arg360, a residue essential for polymerase activity, lies in a solvent-exposed site adjacent to the central pocket. Mutagenesis data and the sucrose-bound structure of inactive levansucrase E342A, at a resolution of 2.1 A, strongly suggest that three conserved acidic side chains in the central pocket are critical for catalysis, and presumably function as nucleophile (Asp86) and general acid (Glu342), or stabilize the transition state (Asp247).

1PT2 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Bacillus_subtilis Bacillus subtilis] with <scene name='pdbligand=SUC:'>SUC</scene> and <scene name='pdbligand=CA:'>CA</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Levansucrase Levansucrase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.4.1.10 2.4.1.10] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1PT2 OCA].  

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