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![[Figure 4]](jc5013fig4mag.jpg)
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Figure 4
Structural superposition of Bt GH92 enzyme–inhibitor complexes reveals extensive diversity beyond the conserved −1 subsite. (a) A previously solved complex of BT3990–MSM overlaid with BT3130–ManI and BT3965–ManI. Glu535/532/533 overlays with Cys399/392/393 and the glycosidic S atom of MSM to form the subsite boundary. The positions of bound ligands, Ca2+ and coordinating amino acids in the −1 subsite are fully conserved. (b) α-1,2-Mannosidase activity in BT3990 is conferred through hydrogen bonding of the +1 mannoside to His584 and Glu585 (hydrogen bonds are shown as dashed lines). (c) The +1 subsite of BT3130–ManI overlaid with MSM. The 580-loop enters the subsite from the left of the figure at a steeper trajectory; while His581 is conserved, no residue equivalent to the major coordinating side chain, Glu585, is present. A unique tryptophan pair at 172 and 198 offer potential for sugar binding. (d) +1 subsite overlay of BT3965–ManI with MSM. Equivalent 570-loop amino acids are conserved; however, these residues are more distantly located. Pro520 (clashing with MSM O6 in this figure), Trp526 and Tyr45 narrow the vertical dimension of the BT3965 binding cavity. |
![[Figure 4]](jc5013fig4.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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