Biogenesis process of quinohemoprotein aminedehydrogenase accompanying multi-step posttranslational modification reactions

肽基内置辅因子是通过同源酶蛋白的翻译后修饰产生的，不像通常的辅因子，其主要是由水溶性维生素生物合成的。在这项研究中，我们专注于一个内置的醌辅因子，醌血红素蛋白胺脱氢酶（QHNDH），含有半胱氨酸醌（CTQ）。革兰氏阴性菌中编码QHNDH的结构基因与附近的几个基因一起构成多顺反子操纵子，统称为qhp。(1)我们已经确定了三个外周基因，qhpFGR，这也是绝对需要的QHNDH生物发生。(2)我们已经分析了QhpE的功能，并发现QhpE是一种非常不寻常的蛋白酶，几乎以一次性的方式切割其底物。(3)我们已经成功地在体外形成的硫醚交联使用过量生产的重组QhpD，只有当它是纯化的，并在厌氧条件下处理。

Peptidyl built-in cofactors are produced by posttranslational modification of the cognate enzyme proteins, unlike ordinary cofactors which are mostly bio-synthesized from water soluble vitamins. In this study, we focused on a built-in quinone cofactor-containing enzyme, quinohemoprotein amine dehydrogenase (QHNDH) that contains cysteine tryptophyl quinone (CTQ). The structural genes encoding QHNDH in Gram-negative bacteria constitute a polycistronic operon together with several nearby genes, which are collectively termed qhp. (1) We have identified three peripheral genes, qhpFGR, that are also absolutely required for the QHNDH biogenesis. (2) We have analyzed the function of QhpE and revealed that QhpE is an extremely unusual protease that cleaves its substrate nearly in a disposable manner. (3) We have succeeded in in vitro formation of thioether cross-links using overproduced recombinant QhpD only if it is purified and handled under anaerobic conditions.