Single-strand DNA-binding protein
Single-strand DNA-binding protein (SSB) is a protein found in Escherichia coli (E. coli) bacteria, that binds to single-stranded regions of deoxyribonucleic acid (DNA).{{cite journal | vauthors = Shishmarev D, Wang Y, Mason CE, Su XC, Oakley AJ, Graham B, Huber T, Dixon NE, Otting G | display-authors = 6 | title = Intramolecular binding mode of the C-terminus of Escherichia coli single-stranded DNA binding protein determined by nuclear magnetic resonance spectroscopy | journal = Nucleic Acids Research | volume = 42 | issue = 4 | pages = 2750–2757 | date = February 2014 | pmid = 24288378 | pmc = 3936761 | doi = 10.1093/nar/gkt1238 }} Single-stranded DNA is produced during all aspects of DNA metabolism: replication, recombination, and repair. As well as stabilizing this single-stranded DNA, SSB proteins bind to and modulate the function of numerous proteins involved in all of these processes.
Active E. coli SSB is composed of four identical 19 kDa subunits. Binding of single-stranded DNA to the tetramer can occur in different "modes", with SSB occupying different numbers of DNA bases depending on a number of factors, including salt concentration. For example, the (SSB)65 binding mode, in which approximately 65 nucleotides of DNA wrap around the SSB tetramer and contact all four of its subunits, is favoured at high salt concentrations in vitro. At lower salt concentrations, the (SSB)35 binding mode, in which about 35 nucleotides bind to only two of the SSB subunits, tends to form. Further work is required to elucidate the functions of the various binding modes in vivo.
Bacterial SSB
{{Infobox protein family
| Symbol = SSB
| Name = SSB
| image = PDB 1v1q EBI.jpg
| width =
| caption = Crystal structure of PriB- a primosomal DNA replication protein of Escherichia coli
| Pfam = PF00436
| Pfam_clan = CL0021
| InterPro = IPR000424
| SMART =
| PROSITE = PDOC00602
| MEROPS =
| SCOP = 1kaw
| TCDB = 3.A.7
| OPM family =
| OPM protein =
| CAZy =
| CDD =
}}
SSB protein domains in bacteria are important in its function of maintaining DNA metabolism, more specifically DNA replication, repair, and recombination.{{cite journal | vauthors = Meyer RR, Laine PS | title = The single-stranded DNA-binding protein of Escherichia coli | journal = Microbiological Reviews | volume = 54 | issue = 4 | pages = 342–380 | date = December 1990 | pmid = 2087220 | pmc = 372786 | doi = 10.1128/MMBR.54.4.342-380.1990 }} It has a structure of three beta-strands to a single six-stranded beta-sheet to form a protein dimer.{{cite journal | vauthors = Raghunathan S, Ricard CS, Lohman TM, Waksman G | title = Crystal structure of the homo-tetrameric DNA binding domain of Escherichia coli single-stranded DNA-binding protein determined by multiwavelength x-ray diffraction on the selenomethionyl protein at 2.9-A resolution | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 94 | issue = 13 | pages = 6652–6657 | date = June 1997 | pmid = 9192620 | pmc = 21213 | doi = 10.1073/pnas.94.13.6652 | doi-access = free }}
See also
References
{{Reflist}}
{{InterPro content|IPR000635}}
External links
- {{MeshName|Single-Stranded+DNA+Binding+Proteins}}
- [https://web.archive.org/web/20120710125521/http://pfam.sanger.ac.uk/family/PF00436 SSB in PFAM]
{{DNA replication}}