Single stranded binding protein: Difference between revisions
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SSB proteins have been identified in many different organisms, but the most well understood SSB remains the SSB of ''E. coli''. ''E. coli'' SSB is a homotetramer consisting of <scene name='56/566528/Homotetramer/1'>four identical subunits</scene> which are each about 19 kDa in size <ref>PMID:2087220</ref>. There are two different binding modes of the ''E. coli'' SSB when it complexes with ssDNA<ref>PMID:11993998</ref>. Regulation of these modes has been found to be dependent on salt concentration, in addition to other unknown factors. Under low salt conditions, the protein is less efficient as only two of the four identical subunits of ''E. coli'' SSB were found to bind to the ssDNA <ref>PMID:11993998</ref>. Under high salt concentrations, however, all four subunits of the homotetramer bind to the ssDNA, increasing the number of nucleotides in contact with the SSB and thus favoring SSB-ssDNA interactions. Depending on the salt concentration and other factors, estimates of the size of the site of interaction between SSB and ssDNA range anywhere from 30 to 73 nucleotides for each tetramer <ref>PMID:11993998</ref>. | SSB proteins have been identified in many different organisms, but the most well understood SSB remains the SSB of ''E. coli''. ''E. coli'' SSB is a homotetramer consisting of <scene name='56/566528/Homotetramer/1'>four identical subunits</scene> which are each about 19 kDa in size <ref>PMID:2087220</ref>. There are two different binding modes of the ''E. coli'' SSB when it complexes with ssDNA<ref>PMID:11993998</ref>. Regulation of these modes has been found to be dependent on salt concentration, in addition to other unknown factors. Under low salt conditions, the protein is less efficient as only two of the four identical subunits of ''E. coli'' SSB were found to bind to the ssDNA <ref>PMID:11993998</ref>. Under high salt concentrations, however, all four subunits of the homotetramer bind to the ssDNA, increasing the number of nucleotides in contact with the SSB and thus favoring SSB-ssDNA interactions. Depending on the salt concentration and other factors, estimates of the size of the site of interaction between SSB and ssDNA range anywhere from 30 to 73 nucleotides for each tetramer <ref>PMID:11993998</ref>. | ||
Active ''E. coli'' SSB is made of a homotetramer with extensive DNA binding domains that bind to <scene name='56/566528/Dna/1'>a single strand of DNA</scene><ref>PMID:2087220</ref>. The tetramers consist of <scene name='56/566528/E_coli_ssb_alpha_helices/1'>α-helices</scene>, β-sheets, and random coils. Each subunit contains an α-helix and several β-sheets. The secondary structure also includes a NH2 terminus, which consists of multiple positively charged amino acids. The DNA-binding domain lies within 115 amino acid residues from this terminus. The COOH terminus includes many acidic amino acids <ref>PMID:2087220</ref>. | Active ''E. coli'' SSB is made of a homotetramer with extensive DNA binding domains that bind to <scene name='56/566528/Dna/1'>a single strand of DNA</scene><ref>PMID:2087220</ref>. The tetramers consist of <scene name='56/566528/E_coli_ssb_alpha_helices/1'>α-helices</scene>, <scene name='56/566528/Beta_sheets/2'>β-sheets</scene>, and random coils. Each subunit contains an α-helix and several β-sheets. The secondary structure also includes a NH2 terminus, which consists of multiple positively charged amino acids. The DNA-binding domain lies within 115 amino acid residues from this terminus. The COOH terminus includes many acidic amino acids <ref>PMID:2087220</ref>. | ||
</StructureSection> | </StructureSection> | ||