How a protein prepares for B12 binding: structure and dynamics of the B12-binding subunit of glutamate mutase from Clostridium tetanomorphum.
How a protein prepares for B12 binding: structure and dynamics of the B12-binding subunit of glutamate mutase from Clostridium tetanomorphum.
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蛋白质如何准备 B12 结合：破伤风梭菌谷氨酸变位酶 B12 结合亚基的结构和动力学。
DOI：
10.1016/s0969-2126(98)00103-8
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Kräutler,B
中科院分区：
文献类型：
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作者：
Tollinger,M;Konrat,R;Hilbert,BH;Marsh,EN;Kräutler,B
背景：谷氨酸变位酶是一种腺苷钴酰胺(辅酶B12)依赖的酶，催化(2S)-谷氨酸可逆重排为(2S，3S)-3-甲基天冬氨酸。该酶由两个亚基组成(53.7kDa和14.8kDa)，其活性形式为α-2-β-2四聚体。被称为MutS的较小的亚基被描述为B12结合成分。结果：通过异核核磁共振研究确定了MutS的溶液结构和重要的动力学性质。MutS在溶液中的全局折叠类似于X-射线结晶学对Escherichia Colimthiine合成酶和丙酸杆菌ShermaniimimylMalonyl CoA变位酶B12结合域的测定。在这两种蛋白质中，组氨酸残基取代了B12辅因子的内源钴配位配体。而在MutS中，含有保守组氨酸残基的蛋白质片段形成了一个非结构化和可移动的延伸环。结论：通过比较两个B12结合域和结合了B12辅因子的B12结合域的晶体结构和载脂蛋白MutS的溶液结构，有助于阐明B12结合的机制。MutS的大部分是为B12结合预先组织的，但B12结合位点本身只有部分形成。在与B12结合时，结合位点的重要元件似乎变得结构化，包括形成裂隙一侧的α螺旋，该裂隙容纳辅因子的核苷酸“尾”。
Background:Glutamate mutase is an adenosylcobamide (coenzyme B12) dependent enzyme that catalyzes the reversible rearrangement of (2S)-glutamate to (2S,3S)-3-methylaspartate. The enzyme fromClostridium tetanomorphumcomprises two subunits (of 53.7 and 14.8 kDa) and in its active form appears to be anα2β2tetramer. The smaller subunit, termed MutS, has been characterized as the B12-binding component. Knowledge on the structure of a B12-binding apoenzyme does not exist.Results:The solution structure and important dynamical aspects of MutS have been determined from a heteronuclear NMR study. The global fold of MutS in solution resembles that determined by X-ray crystallography for the B12-binding domains ofEscherichia colimethionine synthase andPropionibacterium shermaniimethylmalonyl CoA mutase. In these two proteins a histidine residue displaces the endogenous cobalt-coordinating ligand of the B12cofactor. In MutS, however, the segment of the protein containing the conserved histidine residue forms part of an unstructured and mobile extended loop.Conclusions:A comparison of the crystal structures of two B12-binding domains, with bound B12cofactor, and the solution structure of the apoprotein MutS has helped to clarify the mechanism of B12binding. The major part of MutS is preorganized for B12binding, but the B12-binding site itself is only partially formed. Upon binding B12, important elements of the binding site appear to become structured, including anαhelix that forms one side of the cleft accommodating the nucleotide ‘tail' of the cofactor.