# Single-stranded binding protein > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Single-stranded_binding_protein > Markdown URL: https://mediated.wiki/source/Single-stranded_binding_protein.md > Source: https://en.wikipedia.org/wiki/Single-stranded_binding_protein > Source revision: 1335558801 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{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 = }}{{Short description|Class of proteins}} '''Single-stranded binding proteins''' ('''SSBs''') are a class of proteins that have been identified in both viruses and organisms from bacteria to humans. == Viral SSB == {{Infobox protein family | Symbol = Viral_DNA_bp | Name = Viral_DNA_bp | image = PDB 1urj EBI.jpg | width = | caption = Single stranded DNA-binding protein(icp8) from ''herpes simplex'' virus-1 | Pfam = PF00747 | Pfam_clan = | InterPro = IPR000635 | SMART = | PROSITE = | MEROPS = | SCOP = | TCDB = | OPM family = | OPM protein = | CAZy = | CDD = }} Although the overall picture of ''[human](/source/human) [cytomegalovirus](/source/cytomegalovirus)'' (HHV-5) DNA synthesis appears typical of the herpesviruses, some novel features are emerging. ===Structure=== In ICP8, the [herpes simplex virus](/source/herpes_simplex_virus) (HSV-1) [single-strand DNA-binding protein](/source/single-strand_DNA-binding_protein) (ssDNA-binding protein (SSB)), the head consists of the eight [alpha helices](/source/alpha_helix). The front side of the neck region consists of a five-stranded [beta-sheet](/source/beta-sheet) and two alpha helices, whereas the back side is a three-stranded beta-sheet The shoulder part of the [N-terminal](/source/N-terminal) domain contains an alpha-helical and beta-sheet region. The [herpes simplex virus](/source/herpes_simplex_virus) (HSV-1) SSB, ICP8, is a nuclear protein that, along other replication proteins is required for viral DNA replication during lytic infection.{{cite journal|vauthors=Mapelli M, Panjikar S, Tucker PA |title=The crystal structure of the herpes simplex virus 1 ssDNA-binding protein suggests the structural basis for flexible, cooperative single-stranded DNA binding |journal=J Biol Chem |year= 2005 |volume= 280 |issue= 4 |pages= 2990–7 |doi=10.1074/jbc.M406780200 |pmid=15507432|doi-access=free }} ===Mechanism=== Six herpes virus-group-common [gene](/source/gene)s encode [protein](/source/protein)s that likely constitute the [replication](/source/self_replication) fork machinery, including a two-subunit DNA polymerase, a [helicase–primase complex](/source/helicase%E2%80%93primase_complex) and a single-stranded DNA-binding protein.{{cite journal |vauthors=Anders DG, McCue LA |title= The human cytomegalovirus genes and proteins required for DNA synthesis |journal= Intervirology |volume= 39 |issue= 5–6 |pages= 378–88 |year= 1996 |pmid= 9130047 |doi= 10.1159/000150508}} The ''[human](/source/human) [herpesvirus](/source/herpesviridae) 1'' (HHV-1) single-strand DNA-binding protein ICP8 is a 128kDa [zinc](/source/zinc) [metalloprotein](/source/metalloprotein). [Photoaffinity labeling](/source/Photoaffinity_labeling) has shown that the region encompassing [amino acid](/source/amino_acid) residues 368-902 contains the single-strand DNA-binding site of ICP8.{{cite journal |vauthors=White EJ, Boehmer PE |title= Photoaffinity labeling of the herpes simplex virus type-1 single-strand DNA-binding protein (ICP8) with oligodeoxyribonucleotides |journal= Biochem. Biophys. Res. Commun. |volume= 264 |issue= 2 |pages= 493–7 |date=October 1999 |pmid= 10529391 |doi= 10.1006/bbrc.1999.1566 |doi-access= free }} The HHHV-1 UL5, UL8, and UL52 [gene](/source/gene)s encode an essential [heterotrimeric](/source/heterotrimeric) DNA helicase–primase that is responsible for concomitant DNA unwinding and [primer](/source/Primer_(molecular_biology)) synthesis at the [viral](/source/virus) DNA replication fork. ICP8 may stimulate DNA unwinding and enable bypass of cisplatin damaged DNA by recruiting the helicase–primase to the DNA.{{cite journal |vauthors=Tanguy Le Gac N, Villani G, Boehmer PE |title= Herpes simplex virus type-1 single-strand DNA-binding protein (ICP8) enhances the ability of the viral DNA helicase-primase to unwind cisplatin-modified DNA |journal= J. Biol. Chem. |volume= 273 |issue= 22 |pages= 13801–7 |date=May 1998 |pmid= 9593724 |doi= 10.1074/jbc.273.22.13801 |doi-access= free }} ==Bacterial SSB== [SSB protein domains](/source/Single-strand_DNA-binding_protein) in [bacteria](/source/bacteria) are important maintaining [DNA metabolism](/source/DNA_metabolism), more specifically [DNA replication](/source/DNA_replication), repair and recombination.{{cite journal |vauthors=Meyer RR, Laine PS |title=The single-stranded DNA-binding protein of Escherichia coli |journal=Microbiol. Rev. |volume=54 |issue=4 |pages=342–80 |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](/source/beta-sheet) to form a [dimer](/source/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=Proc. Natl. Acad. Sci. U.S.A. |volume=94 |issue=13 |pages=6652–7 |date=June 1997 |pmid=9192620 |pmc=21213 |doi= 10.1073/pnas.94.13.6652|doi-access=free }} ==Eukaryotic replication protein A== {{Infobox heteropolypeptide | heteropolymer = Replication protein A | polymer_type = heterotrimer | protein_type = | function = damaged DNA binding, single-stranded DNA binding | cofactors = | image = 1L1O Replication protein A.png | image_source = This is an image of human Replication protein A. From {{PDB|1L1O}} {{Proteopedia|Replication protein A}} | SubunitCount = 3 | subunit1 = [Replication protein A1](/source/Replication_protein_A1) | gene1 = [RPA1](/source/RPA1) | locus1 = [Chr. 17](/source/Chromosome_17) [https://www.ncbi.nlm.nih.gov/Omim/getmap.cgi?chromosome=17p13.3 p13.3] | subunit2 = [Replication protein A2](/source/Replication_protein_A2) | gene2 = [RPA2](/source/RPA2) | locus2 = [Chr. 1](/source/Chromosome_1) [https://www.ncbi.nlm.nih.gov/Omim/getmap.cgi?chromosome=1p35.3 p35.3] | subunit3 = [Replication protein A3](/source/Replication_protein_A3) | gene3 = [RPA3](/source/RPA3) | locus3 = [Chr. 7](/source/Chromosome_7) [https://www.ncbi.nlm.nih.gov/Omim/getmap.cgi?chromosome=7p21.3 p21.3] }} [Replication protein A](/source/Replication_protein_A) is the functional equivalent of SSB in the nucleus of eukaryotic cells, though there is no sequence homology. ==Eukaryotic mitochondrial SSB== The mitochondria of eukaryotic cells contain their own single stranded DNA binding protein. Human mitochondrial SSB (mtSSB) binds to single-stranded mitochondrial DNA as a tetramer and has sequence similarity to bacterial SSB.{{cite journal|last1=Tiranti|first1=V|last2=Rocchi|first2=M|last3=DiDonato|first3=S|last4=Zeviani|first4=M|title=Cloning of human and rat cDNAs encoding the mitochondrial single-stranded DNA-binding protein (SSB).|journal=Gene|date=30 April 1993|volume=126|issue=2|pages=219–25|pmid=8482537|doi=10.1016/0378-1119(93)90370-i}} Human mtSSB is encoded by the [SSBP1](/source/SSBP1) gene. In yeast, it is encoded by the RIM1 gene.{{cite journal|last1=Van Dyck|first1=E|last2=Foury|first2=F|last3=Stillman|first3=B|last4=Brill|first4=SJ|title=A single-stranded DNA binding protein required for mitochondrial DNA replication in S. cerevisiae is homologous to E. coli SSB.|journal=The EMBO Journal|date=September 1992|volume=11|issue=9|pages=3421–30|pmid=1324172|pmc=556877|doi=10.1002/j.1460-2075.1992.tb05421.x}} ==Role in Genome Repair and Anti-aging== Recently, it has been found that it 1. Helps protect the genome, 2. Is vital for stem cells and 3. Is involved with maintaining telomere length.{{cite journal |last1=Pfeifer |first1=Matthias |last2=Brem |first2=Reto |last3=Lippert |first3=Timothy P. |last4=Boulianne |first4=Bryant |last5=Ho |first5=Howin Ng |last6=Robinson |first6=Mark E. |last7=Stebbing |first7=Justin |last8=Feldhahn |first8=Niklas |title=SSB1/SSB2 Proteins Safeguard B Cell Development by Protecting the Genomes of B Cell Precursors |journal=The Journal of Immunology |date=15 June 2019 |volume=202 |issue=12 |pages=3423–3433 |doi=10.4049/jimmunol.1801618 |pmid=31085591 |pmc=6545462 }}{{cite journal |last1=Shi |first1=Wei |last2=Vu |first2=Therese |last3=Boucher |first3=Didier |last4=Biernacka |first4=Anna |last5=Nde |first5=Jules |last6=Pandita |first6=Raj K. |last7=Straube |first7=Jasmin |last8=Boyle |first8=Glen M. |last9=Al-Ejeh |first9=Fares |last10=Nag |first10=Purba |last11=Jeffery |first11=Jessie |last12=Harris |first12=Janelle L. |last13=Bain |first13=Amanda L. |last14=Grzelak |first14=Marta |last15=Skrzypczak |first15=Magdalena |last16=Mitra |first16=Abhishek |last17=Dojer |first17=Norbert |last18=Crosetto |first18=Nicola |last19=Cloonan |first19=Nicole |last20=Becherel |first20=Olivier J. |last21=Finnie |first21=John |last22=Skaar |first22=Jeffrey R. |last23=Walkley |first23=Carl R. |last24=Pandita |first24=Tej K. |last25=Rowicka |first25=Maga |last26=Ginalski |first26=Krzysztof |last27=Lane |first27=Steven W. |last28=Khanna |first28=Kum Kum |title=Ssb1 and Ssb2 cooperate to regulate mouse hematopoietic stem and progenitor cells by resolving replicative stress |journal=Blood |date=4 May 2017 |volume=129 |issue=18 |pages=2479–2492 |doi=10.1182/blood-2016-06-725093 |pmid=28270450 |pmc=5418634 }}{{cite journal |last1=Pandita |first1=R. K. |last2=Chow |first2=T. T. |last3=Udayakumar |first3=D. |last4=Bain |first4=A. L. |last5=Cubeddu |first5=L. |last6=Hunt |first6=C. R. |last7=Shi |first7=W. |last8=Horikoshi |first8=N. |last9=Zhao |first9=Y. |last10=Wright |first10=W. E. |last11=Khanna |first11=K. K. |last12=Shay |first12=J. W. |last13=Pandita |first13=T. K. |title=Single-Strand DNA-Binding Protein SSB1 Facilitates TERT Recruitment to Telomeres and Maintains Telomere G-Overhangs |journal=Cancer Research |date=14 January 2015 |volume=75 |issue=5 |pages=858–869 |doi=10.1158/0008-5472.CAN-14-2289 |pmid=25589350 |pmc=4351820 }} ==See also== * [DNA-binding protein](/source/DNA-binding_protein) * [Replication protein A](/source/Replication_protein_A) * [Comparison of nucleic acid simulation software](/source/Comparison_of_nucleic_acid_simulation_software) ==References== {{Reflist}} {{InterPro content|IPR000635}} ==External links== * {{MeshName|Single-Stranded+DNA+Binding+Proteins}} * [http://pfam.sanger.ac.uk/family/PF00436 SSB in PFAM] {{Webarchive|url=https://web.archive.org/web/20120710125521/http://pfam.sanger.ac.uk/family/PF00436 |date=2012-07-10 }} {{DNA replication}} Category:Protein families Category:DNA replication Category:Proteins Category:DNA-binding substances --- Adapted from the Wikipedia article [Single-stranded binding protein](https://en.wikipedia.org/wiki/Single-stranded_binding_protein) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Single-stranded_binding_protein?action=history)). 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