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Binding of regulatory protein omega from Streptococcus pyogenes plasmid pSM19035 to direct and inverted 7-base pair repeats of operator DNA

Item Type:Article
Title:Binding of regulatory protein omega from Streptococcus pyogenes plasmid pSM19035 to direct and inverted 7-base pair repeats of operator DNA
Creators Name:Dostal, L. and Pratto, F. and Alonso, J.C. and Welfle, H.
Abstract:pSM19035-encoded dimeric regulator omega (omega2) belongs to the MetJ/Arc family of ribbon-helix-helix DNA binding proteins. omega2 binds to a set of unspaced 7-base pair repeat units with sequence 5'-A/TATCACA/T-3'. Protein omega2 and its variant omega2deltaN18, lacking the first 18 N-terminal amino acids, bind poorly to one heptad DNA, but the affinity to DNA markedly increases with two and more heptads organized in direct or inverted orientation. Raman difference spectra indicate that omega2 and omega2deltaN18 bind to operator DNA in the major groove and contact thymine, adenine and guanine residues. The mode of omega2 or omega2deltaN18 interaction with operator DNA is not affected by the orientation and number of heptads. The Raman data of omega2T29A, an omega2 variant with Ala instead of Thr at position 29 of the beta-sheet, show a sequence-independent binding mode to DNA, which differs from the binding mode of wt omega2 protein to its cognate site. The Raman data strongly support the notion that the 18 N-terminal amino acids are not required for omega2 activity, whereas Thr29 plays an essential role for operator DNA binding. The data suggest the formation of a hydrogen bond between Thr29 of wild-type omega2 to one of the bases in the central 5'-TCA-3'/5'-TGA-3' stretch of the 7-bp binding site.
Keywords:Transcriptional repressor, omega-protein, Ribbon-helix-helix proteins, Protein-DNA interaction, Raman difference spectra
Source:Journal of Raman Spectroscopy
ISSN:0377-0486
Publisher:John Wiley & Sons (U.K.)
Volume:38
Number:2
Page Range:166-175
Date:February 2007
Official Publication:https://doi.org/10.1002/jrs.1619

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