Structural and enzymatic analysis of MshA from Corynebacterium glutamicum -: Substrate-assisted catalysis
Structural and enzymatic analysis of MshA from Corynebacterium glutamicum -: Substrate-assisted catalysis
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DOI：
10.1074/jbc.m801017200
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发表时间：
2008-06-06
影响因子：
4.8
通讯作者：
Blanchard, John S.
中科院分区：
文献类型：
--
作者：
Vetting, Matthew W.;Frantom, Patrick A.;Blanchard, John S.
在真菌硫醇生物合成的第一步，糖基转移酶MshA催化n -乙酰氨基葡萄糖胺从udp - n -乙酰氨基葡萄糖胺转移到1- l-肌醇-1-磷酸。在没有底物和与UDP和1- l-肌醇-1-磷酸配合物的情况下，测定了谷氨酸棒状杆菌MshA的结构。MshA属于GT-B结构族，其成员具有双结构域，两个结构域均表现为罗斯曼型褶皱。供体糖与c端结构域的结合使n端结构域相对于c端结构域旋转97度，抑制UDP并产生1- l-肌醇-1-磷酸的结合位点。该结构突出了在结合udp - n -乙酰氨基葡萄糖和1- l-肌醇-1-磷酸中重要的残基。三元配合物的分子模型表明，底物udp - n -乙酰氨基葡萄糖的β -磷酸促进1- l-肌醇-1-磷酸3-羟基的亲核攻击，同时促进糖核苷酸键的裂解。
The glycosyltransferase termed MshA catalyzes the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine to 1-L-myo-inositol-1-phosphate in the first committed step of mycothiol biosynthesis. The structure of MshA from Corynebacterium glutamicum was determined both in the absence of substrates and in a complex with UDP and 1-L-myo-inositol-1-phosphate. MshA belongs to the GT-B structural family whose members have a two-domain structure with both domains exhibiting a Rossman-type fold. Binding of the donor sugar to the C-terminal domain produces a 97 degrees rotational reorientation of the N-terminal domain relative to the C-terminal domain, clamping down on UDP and generating the binding site for 1-L-myoinositol-1-phosphate. The structure highlights the residues important in binding of UDP-N-acetylglucosamine and 1-L-myo-inositol-1-phosphate. Molecular models of the ternary complex suggest a mechanism in which the beta-phosphate of the substrate, UDP-N-acetylglucosamine, promotes the nucleophilic attack of the 3-hydroxyl group of 1-L-myo-inositol-1-phosphate while at the same time promoting the cleavage of the sugar nucleotide bond.