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

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 function...

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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
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Summary:	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.
Bibliography:	Funding information National Institutes of Health, Grant/Award Number: GM100156 Wenfei Ding and Hui Yin Tan contributed equally to this study. ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Funding information National Institutes of Health, Grant/Award Number: GM100156
ISSN:	0961-8368 1469-896X
DOI:	10.1002/pro.3855