NDP-forming type acyl-CoA synthetase superfamily proteins are known to have six essential subdomains (1, 2, 3, a, b, c) of which partition and order are varied, suggesting yet-to-be-defined subdomain rearrangement happened in its evolution. Comparison in physicochemical and biochemical characteristics between the recombinant proteins which we made from fragmented subdomains and wild-type protein, acetate-CoA ligase in a hyperthermophilic archaeon, consisting of two distinct subunits (α1-2-3 and βa-b-c) provided a clue to the mystery of its molecular evolutionary passage. Although solubility and thermostability of each fragmented subdomain turned out to be lower than that of wild-type, mixture of the three synthetic subunits of α1-2, α3, and βa-b-c had quaternary structure, thermostability, and enzymatic activity comparable to those of the wild-type. This suggests that substantial independence and mobility of subdomain 3 have enabled rearrangement of the subdomains; and thermostability of the subdomains has constrained the composition of the subunits.

已知NDP形成型酰基辅酶A合成酶超家族蛋白具有六个必不可少的亚结构域（1、2、3，a，b，c），其分区和顺序是变化的，表明尚未确定的亚结构域重排发生在它的演变。比较由片段化的子域和野生型蛋白质，由两个不同亚基（α1-2-3和βa-bc组成）的野生型蛋白质乙酸盐-CoA连接酶在理化和生化特性方面的比较它的分子进化通道之谜。尽管每个片段化亚域的溶解度和热稳定性均低于野生型，但α1-2，α3和βa-bc的三个合成亚基的混合物具有四级结构，热稳定性，和酶活性与野生型相当。这表明子域3的基本独立性和可移动性使得能够重新排列子域。亚域的热稳定性限制了亚基的组成。