Wadsworth R I, White M F
Centre for Biomolecular Science, University of St Andrews, North Haugh, St Andrews, Fife KY16 9ST, UK.
Nucleic Acids Res. 2001 Feb 15;29(4):914-20. doi: 10.1093/nar/29.4.914.
Single-stranded DNA binding proteins (SSBs) play central roles in cellular and viral processes involving the generation of single-stranded DNA. These include DNA replication, homologous recombination and DNA repair pathways. SSBs bind DNA using four 'OB-fold' (oligonucleotide/oligosaccharide binding fold) domains that can be organised in a variety of overall quaternary structures. Thus eubacterial SSBs are homotetrameric whilst the eucaryal RPA protein is a heterotrimer and euryarchaeal proteins vary significantly in their subunit compositions. We demonstrate that the crenarchaeal SSB protein is an abundant protein with a unique structural organisation, existing as a monomer in solution and multimerising on DNA binding. The protein binds single-stranded DNA distributively with a binding site size of approximately 5 nt per monomer. Sulfolobus SSB lacks the zinc finger motif found in the eucaryal and euryarchaeal proteins, possessing instead a flexible C-terminal tail, sensitive to trypsin digestion, that is not required for DNA binding. In comparison with Escherichia coli SSB, the tail may play a role in protein-protein interactions during DNA replication and repair.
单链DNA结合蛋白(SSB)在涉及单链DNA生成的细胞和病毒过程中发挥核心作用。这些过程包括DNA复制、同源重组和DNA修复途径。SSB利用四个“OB折叠”(寡核苷酸/寡糖结合折叠)结构域结合DNA,这些结构域可以以多种整体四级结构组织。因此,真细菌的SSB是同四聚体,而真核生物的RPA蛋白是异三聚体,广古菌的蛋白在亚基组成上有很大差异。我们证明,泉古菌的SSB蛋白是一种丰富的蛋白,具有独特的结构组织,在溶液中以单体形式存在,在结合DNA时多聚化。该蛋白以分散的方式结合单链DNA,每个单体的结合位点大小约为5个核苷酸。嗜热栖热菌SSB缺乏真核生物和广古菌蛋白中发现的锌指基序,取而代之的是一个对胰蛋白酶消化敏感的柔性C末端尾巴,DNA结合不需要该尾巴。与大肠杆菌SSB相比,该尾巴可能在DNA复制和修复过程中的蛋白质-蛋白质相互作用中发挥作用。