Structural insights into the mechanism of four-coordinate Cob(II)alamin formation in the active site of the Salmonella enterica ATP:Co(I)rrinoid adenosyltransferase enzyme: critical role of residues Phe91 and Trp93.
Structural insights into the mechanism of four-coordinate Cob(II)alamin formation in the active site of the Salmonella enterica ATP:Co(I)rrinoid adenosyltransferase enzyme: critical role of residues Phe91 and Trp93.
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在肠沙门氏菌ATP的活性部位：CO（i）rrinoid腺基转移酶的活性部位中四坐标蛋白（II）alamin形成机制的结构见解：残基PHE91和TRP93的关键作用的关键作用。
DOI：
10.1021/bi301378d
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发表时间：
2012-12-04
期刊：
影响因子：
2.9
通讯作者：
Escalante-Semerena JC
中科院分区：
文献类型：
--
作者：
Moore TC;Newmister SA;Rayment I;Escalante-Semerena JC
ATP：Co（I）类核昔酸腺苷转移酶（ACATs）是催化钴胺素和ATP形成腺苷钴胺素（腺苷钴胺素Cbl，辅酶B12）的酶。ACATs有三个家族，即CobA、EutT和PduO。在肠道沙门氏菌中，CobA是从头合成β-Cbl和从环境中回收不完全前体和钴胺素所需的管家酶。在这里，我们报告的晶体结构的钴A与ATP，四坐标钴胺素，五坐标钴胺素。这提供了第一个晶体学证据的存在，cob（II）alamin的活性位点的钴A。该结构表明了一种机制，其中该酶采用封闭构象和两个残基，Phe 91和Trp 93，取代5，6-二甲基苯并咪唑（DMB），钴胺素的较低的核苷酸配体碱基，产生一个短暂的四配位钴胺素，这是至关重要的形成cobal-Cbl Co-C键。Phe 91和Trp 93的体内和体外突变分析强调了活性位点中庞大的疏水侧链的重要作用。所提出的CobA增加cob（II）alamin/cob（I）alamin对的氧化还原电位以促进Co-C键形成的方式似乎类似于PduO型ACATs所利用的方式，其中在两种情况下，通过将咕啉环的该面邻近于大体积疏水侧链的簇来消除低级配体与钴离子的极性配位。
ATP:Co(I)rrinoid adenosyltransferases (ACATs) are enzymes that catalyze the formation of adenosylcobalamin (AdoCbl, coenzyme B12) from cobalamin and ATP. There are three families of ACATs, namely CobA, EutT and PduO. In Salmonella enterica, CobA is the housekeeping enzyme that is required for de novo AdoCbl synthesis and for salvaging incomplete precursors and cobalamin from the environment. Here, we report the crystal structure of CobA in complex with ATP, four-coordinate cobalamin, and five-coordinate cobalamin. This provides the first crystallographic evidence for the existence of cob(II)alamin in the active site of CobA. The structure suggests a mechanism in which the enzyme adopts a closed conformation and two residues, Phe91 and Trp93, displace 5,6-dimethylbenzimidazole (DMB), the lower nucleotide ligand base of cobalamin, to generate a transient four-coordinate cobalamin, which is critical in the formation of the AdoCbl Co-C bond. In vivo and in vitro mutational analysis of Phe91 and Trp93 emphasize the important role of bulky hydrophobic side chains in the active site. The proposed manner in which CobA increases the redox potential of the cob(II)alamin/cob(I)alamin couple to facilitate formation of the Co-C bond appears to be analogous to that utilized by the PduO-type ACATs, where in both cases the polar coordination of the lower ligand to the cobalt ion is eliminated by placing that face of the corrin ring adjacent to a cluster of bulky hydrophobic side chains.
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DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
15
作者：
Liu, DH;Williamson, DA;Benson, DR
通讯作者：
Benson, DR
影响因子：
2.9
作者：
Mera, Paola E.;St Maurice, Martin;Escalante-Semerena, Jorge C.
通讯作者：
Escalante-Semerena, Jorge C.
影响因子：
3.2
作者：
Buan, NR;Suh, SJ;Escalante-Semerena, JC
通讯作者：
Escalante-Semerena, JC
影响因子：
1.6
作者：
Blommel, Paul G.;Fox, Brian G.
通讯作者：
Fox, Brian G.