The Escherichia coli single-strand DNA binding protein (SSB) is essential to viability where it functions to regulate SSB interactome function. Here it binds to single-stranded DNA and to target proteins that comprise the interactome. The region of SSB that links these two essential protein functions is the intrinsically disordered linker. Key to linker function is the presence of three, conserved PXXP motifs that mediate binding to oligosaccharide-oligonucleotide binding folds (OB-fold) present in SSB and its interactome partners. Not surprisingly, partner OB-fold deletions eliminate SSB binding. Furthermore, single point mutations in either the PXXP motifs or, in the RecG OB-fold, obliterate SSB binding. The data also demonstrate that, and in contrast to the view currently held in the field, the C-terminal acidic tip of SSB is not required for interactome partner binding. Instead, we propose the tip has two roles. First, and consistent with the proposal of Dixon, to regulate the structure of the C-terminal domain in a biologically active conformation that prevents linkers from binding to SSB OB-folds until this interaction is required. Second, as a secondary binding domain. Finally, as OB-folds are present in SSB and many of its partners, we present the SSB interactome as the first family of OB-fold genome guardians identified in prokaryotes.

中文翻译：

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单链结合蛋白-RecG 结合的机制：对 SSB 相互作用组功能的影响。


大肠杆菌单链 DNA 结合蛋白 (SSB) 对于生存至关重要，它的作用是调节 SSB 相互作用组功能。在这里，它与单链 DNA 和构成相互作用组的靶蛋白结合。连接这两个基本蛋白质功能的 SSB 区域是本质上无序的连接子。连接子功能的关键是存在三个保守的 PXXP 基序，这些基序介导与 SSB 及其相互作用组伙伴中存在的寡糖-寡核苷酸结合折叠 (OB 折叠) 的结合。毫不奇怪，伙伴 OB 折叠缺失消除了 SSB 结合。此外，PXXP 基序或 RecG OB 折叠中的单点突变会消除 SSB 结合。数据还表明，与该领域目前的观点相反，SSB 的 C 端酸性尖端对于相互作用组配偶体结合来说不是必需的。相反，我们建议该尖端有两个作用。首先，与 Dixon 的提议一致，以生物活性构象调节 C 端结构域的结构，防止接头与 SSB OB 折叠结合，直到需要这种相互作用。其次，作为第二结合域。最后，由于 OB 折叠存在于 SSB 及其许多伙伴中，我们将 SSB 相互作用组作为原核生物中鉴定的第一个 OB 折叠基因组守护者家族。