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Publication Abstract from PubMed

Following the discovery of an exo-1,3/1,4-beta-glucanase (glycoside hydrolase family 3) from a seaweed-associated bacterium Pseudoalteromonas sp. BB1, the recombinant three-domain protein (ExoP) was crystallized and its structure solved to 2.3A resolution. The first two domains of ExoP, both of which contribute to the architecture of the active site, are similar to those of the two-domain barley homologue ExoI with a distinctive Trp-Trp clamp at the +1 subsite, although ExoI displays broader specificity towards beta-glycosidic linkages. Notably excision of the third domain of ExoP results in an inactive enzyme. Domain 3 has a beta-sandwich structure and was shown by circular dichroism to be more temperature stable than the native enzyme. It makes relatively few contacts to domain 1 and none at all to domain 2. Two of the domain 3 residues involved at the interface, Q683 (forming one hydrogen bond) and Q676 (forming two) were mutated to alanine. Variant Q676A retained about half the activity of native ExoP but the Q683A variant was severely attenuated. The crystal structure of Q683A-ExoP indicated that domain 3 was highly mobile and that Q683 is critical to the stabilization of ExoP by domain 3. SAXS data lent support to this proposal. Domain 3 does not appear to be an obvious carbohydrate binding domain and is related neither in sequence nor structure to the additional domains characterized in other GH3 subgroups. Its major role appears to be for protein stability but it may also help orient substrate.

Structure and activity of exo-1,3/1,4-beta-glucanase from marine bacterium Pseudoalteromonas sp. BB1 showing a novel C-terminal domain.,Nakatani Y, Cutfield SM, Cowieson NP, Cutfield JF FEBS J. 2011 Nov 29. doi: 10.1111/j.1742-4658.2011.08439.x. PMID:22129429^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.