Department of Biochemistry, Bose Institute P-1/12, C.I.T. Scheme VIIM, Kolkata 700 054, India.
Arch Biochem Biophys. 2010 Sep 15;501(2):239-43. doi: 10.1016/j.abb.2010.06.030. Epub 2010 Jul 3.
LambdaCII is the key protein that influences the lysis/lysogeny decision of lambda by activating several phage promoters. The effect of CII is modulated by a number of phage and host proteins including Escherichia coli HflK and HflC. These membrane proteins copurify as a tightly bound complex 'HflKC' that inhibits the HflB (FtsH)-mediated proteolysis of CII both in vitro and in vivo. Individual purification of HflK and HflC has not been possible so far, since each requires the presence of the other for proper folding. We report the first purification of HflK and HflC separately as active and functional proteins and show that each can interact with HflB on its own and each inhibits the proteolysis of CII. They also inhibit the proteolysis of E. coli sigma(32) by HflB. We show that at low concentrations each protein is dimeric, based on which we propose a scheme for the mutual interactions of HflB, HflK and HflC in a supramolecular HflBKC protease complex.
LambdaCII 是影响 lambda 裂解/溶源决定的关键蛋白，它可以激活几个噬菌体启动子。CII 的作用受多种噬菌体和宿主蛋白的调节，包括大肠杆菌 HflK 和 HflC。这些膜蛋白作为一个紧密结合的复合物“ HflKC”共纯化，该复合物在体外和体内均抑制 HflB（FtsH）介导的 CII 蛋白水解。到目前为止，尚未能够单独纯化 HflK 和 HflC，因为每个蛋白的正确折叠都需要另一个蛋白的存在。我们报告了 HflK 和 HflC 的首次单独分离，它们是活性和功能性蛋白，并表明它们都可以与 HflB 相互作用，并且都可以抑制 CII 的蛋白水解。它们还抑制 HflB 对大肠杆菌 sigma(32)的蛋白水解。我们发现，在低浓度下，每种蛋白都是二聚体，基于此，我们提出了 HflB、HflK 和 HflC 在超分子 HflBKC 蛋白酶复合物中的相互作用方案。
