Locking mechanism preventing radical damage in the absence of substrate,, as revealed by the x-ray structure of lysine 5,6-aminomutase
Locking mechanism preventing radical damage in the absence of substrate,, as revealed by the x-ray structure of lysine 5,6-aminomutase
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DOI：
10.1073/pnas.0407074101
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发表时间：
2004-11-09
影响因子：
11.1
通讯作者：
Drennan, CL
中科院分区：
文献类型：
--
作者：
Berkovitch, F;Behshad, E;Drennan, CL
赖氨酸5，6-氨基变位酶是腺苷钴胺素和吡哆醛5 '-磷酸依赖性酶，催化DL-赖氨酸和L-β-赖氨酸末端氨基的1，2重排。我们已经解决了从斯氏梭菌赖氨酸-5，6-氨基变位酶的无底物形式的X-射线结构。在这种结构中，Rossmann结构域通过赖氨酸144共价结合吡哆醛-5 '-磷酸，并将其定位在邻近磷酸丙糖异构酶桶结构域的推定活性位点，同时将另一辅因子腺苷钴胺素定位在离活性位点约25埃处。在吡哆醛-5 '-磷酸结合的这种模式中，辅因子充当锚，将Rossmann结构域的单独多肽链拴系到磷酸丙糖异构酶桶结构域。在底物结合和赖氨酸-144键的transaldimination后，Rossmann结构域将自由旋转并使腺苷钴胺素、吡哆醛-5 '-磷酸和底物接近。因此，该结构体现了一种锁定机制，以使腺苷钴胺素远离活性位点并防止在没有底物的情况下产生自由基。
Lysine 5,6-aminomutase is an adenosylcobalamin and pyridoxal5'-phosphate-dependent enzyme that catalyzes a 1,2 rearrangement of the terminal amino group of DL-lysine and of L-beta-lySine. We have solved the x-ray structure of a substrate-free form of lysine-5,6-aminomutase from Clostridium sticklandii. In this structure, a Rossmann domain covalently binds pyridoxal-5'-phosphate by means of lysine 144 and positions it into the putative active site of a neighboring triosephosphate isomerase barrel domain, while simultaneously positioning the other cofactor, adenosylcobalamin, approximate to25 Angstrom from the active site. In this mode of pyridoxal-5'-phosphate binding, the cofactor acts as an anchor, tethering the separate polypeptide chain of the Rossmann domain to the triosephosphate isomerase barrel domain. Upon substrate binding and transaldimination of the lysine-144 linkage, the Rossmann domain would be free to rotate and bring adenosylcobalamin, pyridoxal-5'-phosphate, and substrate into proximity. Thus, the structure embodies a locking mechanism to keep the adenosylcobalamin out of the active site and prevent radical generation in the absence of substrate.