Structural Basis of the Inhibition of Golgi -Mannosidase II by Mannostatin A and the Role of the Thiomethyl Moiety in Ligand-Protein
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- 作者：Sameer P. Kawatkar ; Douglas A. Kuntz ; Robert J. Woods ; David R. Rose ; and Geert-Jan Boons
- 刊名：Journal of the American Chemical Society
- 出版年：2006
- 出版时间：June 28, 2006
- 年：2006
- 卷：128
- 期：25
- 页码：8310 - 8319
- 全文大小：564K
- 年卷期：v.128,no.25(June 28, 2006)
- ISSN：1520-5126
文摘
The X-ray crystal structures of mannose trimming enzyme drosophila Golgi 
-mannosidase II(dGMII) complexed with the inhibitors mannostatin A (1) and an N-benzyl analogue (2) have beendetermined. Molecular dynamics simulations and NMR studies have shown that the five-membered ring ofmannostatin A is rather flexible occupying pseudorotational itineraries between 2T3 and 5E, and 2T3 and 4E.In the bound state, mannostatin A adopts a 2T1 twist envelope conformation, which is not significantlypopulated in solution. Possible conformations of the mannosyl oxacarbenium ion and an enzyme-linkedintermediate have been compared to the conformation of mannostatin A in the cocrystal structure withdGMII. It has been found that mannostatin A best mimics the covalent linked mannosyl intermediate, whichadopts a 1S5 skew boat conformation. The thiomethyl group, which is critical for high affinity, superimposeswith the C-6 hydroxyl of the covalent linked intermediate. This functionality is able to make a number ofadditional polar and nonpolar interactions increasing the affinity for dGMII. Furthermore, the X-ray structuresshow that the environment surrounding the thiomethyl group of 1 is remarkably similar to the arrangementsaround the methionine residues in the protein. Collectively, our studies contradict the long held view thatpotent inhibitors of glycosidases must mimic an oxacarbenium ion like transition state.
-mannosidase II(dGMII) complexed with the inhibitors mannostatin A (1) and an N-benzyl analogue (2) have beendetermined. Molecular dynamics simulations and NMR studies have shown that the five-membered ring ofmannostatin A is rather flexible occupying pseudorotational itineraries between 2T3 and 5E, and 2T3 and 4E.In the bound state, mannostatin A adopts a 2T1 twist envelope conformation, which is not significantlypopulated in solution. Possible conformations of the mannosyl oxacarbenium ion and an enzyme-linkedintermediate have been compared to the conformation of mannostatin A in the cocrystal structure withdGMII. It has been found that mannostatin A best mimics the covalent linked mannosyl intermediate, whichadopts a 1S5 skew boat conformation. The thiomethyl group, which is critical for high affinity, superimposeswith the C-6 hydroxyl of the covalent linked intermediate. This functionality is able to make a number ofadditional polar and nonpolar interactions increasing the affinity for dGMII. Furthermore, the X-ray structuresshow that the environment surrounding the thiomethyl group of 1 is remarkably similar to the arrangementsaround the methionine residues in the protein. Collectively, our studies contradict the long held view thatpotent inhibitors of glycosidases must mimic an oxacarbenium ion like transition state.