Krüer Markus, Haumann Michael, Meyer-Klaucke Wolfram, Thauer Rudolf K, Dau Holger
Max-Planck-Institut für terrestrische Mikrobiologie and Laboratorium für Mikrobiologie, Fachbereich Biologie der Philipps-Universität, Marburg, Germany.
Eur J Biochem. 2002 Apr;269(8):2117-23. doi: 10.1046/j.1432-1033.2002.02860.x.
Methanol:coenzyme M methyltransferase from methanogenic archaea is a cobalamin-dependent enzyme composed of three different subunits: MtaA, MtaB and MtaC. MtaA is a zinc protein that catalyzes the methylation of coenzyme M (HS-CoM) with methylcob(III)alamin. We report zinc XAFS (X-ray absorption fine structure) results indicating that, in the absence of coenzyme M, zinc is probably coordinated by a single sulfur ligand and three oxygen or nitrogen ligands. In the presence of coenzyme M, one (N/O)-ligand was replaced by sulfur, most likely due to ligation of the thiol group of coenzyme M. Mutations in His237 or Cys239, which are proposed to be involved in ligating zinc, resulted in an over 90% loss in enzyme activity and in distinct changes in the zinc ligands. In the His237-->Ala and Cys239-->Ala mutants, coenzyme M also seemed to bind efficiently by ligation to zinc indicating that some aspects of the zinc ligand environment are surprisingly uncritical for coenzyme M binding.
产甲烷古菌中的辅酶M甲基转移酶是一种依赖钴胺素的酶，由三个不同的亚基组成：MtaA、MtaB和MtaC。MtaA是一种锌蛋白，它催化辅酶M（HS-CoM）与甲基钴胺（III）的甲基化反应。我们报告了锌X射线吸收精细结构（XAFS）结果，表明在没有辅酶M的情况下，锌可能由一个硫配体和三个氧或氮配体配位。在有辅酶M的情况下，一个（N/O）配体被硫取代，最有可能是由于辅酶M的巯基的配位作用。His237或Cys239中的突变被认为参与锌的配位，导致酶活性损失超过90%，并且锌配体发生明显变化。在His237→Ala和Cys239→Ala突变体中，辅酶M似乎也能通过与锌的配位有效结合，这表明锌配体环境的某些方面对于辅酶M的结合出人意料地不重要。
