The mechanism of Single strand binding protein–RecG binding: Implications for SSB interactome function

• Published in: Protein science Vol. 29; no. 5; pp. 1211 - 1227
• Main Authors: Ding, Wenfei, Tan, Hui Yin, Zhang, Jia Xiang, Wilczek, Luke A., Hsieh, Karin R., Mulkin, Jeffrey A., Bianco, Piero R.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-05-2020; Wiley Subscription Services, Inc
• Subjects: Binding Sites; Biological activity; Deoxyribonucleic acid; DNA; DNA helicase; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; Domains; E coli; Escherichia coli Proteins - chemistry; Escherichia coli Proteins - genetics; Genomes; Models, Molecular; Mutation; OB‐fold; Oligonucleotides; Oligonucleotides - chemistry; Oligosaccharides; Oligosaccharides - chemistry; Point Mutation; Prokaryotes; Protein structure; Proteins; PXXP motif; RecG; SH3 domain; single‐strand binding protein; SSB interactome; DNA helicase; SH3 domain; SSB interactome; RecG; single-strand binding protein; OB-fold; PXXP motif
• DOI: 10.1002/pro.3855
• EISSN: 1469-896X
• ISSN: 0961-8368

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.