Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, 9600 Gudelsky Drive, Rockville, MD 20850, USA.
Extremophiles. 2011 Mar;15(2):245-52. doi: 10.1007/s00792-010-0352-1. Epub 2011 Jan 28.
Minichromosome maintenance (MCM) helicases are thought to function as the replicative helicases in archaea and eukarya, unwinding the duplex DNA in the front of the replication fork. The archaeal MCM helicase can be divided into three parts, the N-terminal, catalytic, and C-terminal regions. The N-terminal part of the protein is divided into three domains, A, B, and C, and was shown to be involved in protein multimerization and binding to single- and double-stranded DNA. Two Asp residues found in domain C are conserved among MCM proteins from different archaea. These residues are located in a loop at the interface with domain A. Mutations of these residues in the Methanothermobacter thermautotrophicus MCM protein, Asp202 and Asp203, to Asn result in a significant reduction in the ability of the enzyme to bind DNA and in lower thermal stability. However, the mutant proteins retained helicase and ATPase activities. Further investigation of the DNA binding revealed that the presence of ATP rescues the DNA binding deficiencies by these mutant proteins. Possible roles of these conserved residues in MCM function are discussed.
微小染色体维持（MCM）解旋酶被认为在古菌和真核生物中作为复制解旋酶发挥作用，解开复制叉前沿的双链 DNA。古菌 MCM 解旋酶可分为三个部分，N 端、催化和 C 端区域。该蛋白的 N 端部分分为三个结构域 A、B 和 C，被证明参与蛋白质多聚化以及与单链和双链 DNA 的结合。在不同古菌的 MCM 蛋白中发现的结构域 C 中的两个天冬氨酸残基保守。这些残基位于与结构域 A 的界面上的环中。将产甲烷菌 Thermautotrophicus MCM 蛋白中的这些残基天冬氨酸 202 和天冬氨酸 203 突变为天冬酰胺，会导致酶与 DNA 的结合能力显著降低，热稳定性降低。然而，突变蛋白保留了解旋酶和 ATP 酶活性。进一步研究 DNA 结合发现，这些突变蛋白的 DNA 结合缺陷可以通过 ATP 的存在得到挽救。讨论了这些保守残基在 MCM 功能中的可能作用。
