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| {{STRUCTURE_2bnz| PDB=2bnz | SCENE= }} | | {{STRUCTURE_2bnz| PDB=2bnz | SCENE= }} |
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| '''STRUCTURAL BASIS FOR COOPERATIVE BINDING OF RIBBON-HELIX-HELIX OMEGA REPRESSOR TO INVERTED DNA HEPTAD REPEATS'''
| | ===STRUCTURAL BASIS FOR COOPERATIVE BINDING OF RIBBON-HELIX-HELIX OMEGA REPRESSOR TO INVERTED DNA HEPTAD REPEATS=== |
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| ==Overview==
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| Repressor omega regulates transcription of genes required for copy number control, accurate segregation and stable maintenance of inc18 plasmids hosted by Gram-positive bacteria. omega belongs to homodimeric ribbon-helix-helix (RHH2) repressors typified by a central, antiparallel beta-sheet for DNA major groove binding. Homodimeric omega2 binds cooperatively to promotors with 7 to 10 consecutive non-palindromic DNA heptad repeats (5'-(A)/(T)ATCAC(A)/(T)-3', symbolized by -->) in palindromic inverted, converging (--><--) or diverging (<---->) orientation and also, unique to omega2 and contrasting other RHH2 repressors, to non-palindromic direct (-->-->) repeats. Here we investigate with crystal structures how omega2 binds specifically to heptads in minimal operators with (-->-->) and (--><--) repeats. Since the pseudo-2-fold axis relating the monomers in omega(2) passes the central C-G base pair of each heptad with approximately 0.3 A downstream offset, the separation between the pseudo-2-fold axes is exactly 7 bp in (-->-->), approximately 0.6 A shorter in (--><--) but would be approximately 0.6 A longer in (<---->). These variations grade interactions between adjacent omega2 and explain modulations in cooperative binding affinity of omega2 to operators with different heptad orientations.
| | The line below this paragraph, {{ABSTRACT_PUBMED_16528102}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 16528102 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_16528102}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Rhh]] | | [[Category: Rhh]] |
| [[Category: Ribbon-helix-helix]] | | [[Category: Ribbon-helix-helix]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 20:33:11 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 21:49:28 2008'' |
