title: Modulation of Ultrafast Conformational Dynamics in Allosteric Interaction of Gal Repressor Protein with Different Operator DNA Sequences.
abstract: Although all forms of dynamical behaviour of a protein under allosteric interaction with effectors are predicted, little evidence of ultrafast dynamics in the interaction has been reported. Here, we demonstrate the efficacy of a combined approach involving picosecond-resolved FRET and polarisation-gated fluorescence for the exploration of ultrafast dynamics in the allosteric interaction of the Gal repressor (GalR) protein dimer with DNA operator sequences OE and OI . FRET from the single tryptophan residue to a covalently attached probe IAEDANS at a cysteine residue in the C-terminal domain of GalR shows structural perturbation and conformational dynamics during allosteric interaction. Polarisation-gated fluorescence spectroscopy of IAEDANS and another probe (FITC) covalently attached to the operator directly revealed the essential dynamics for cooperativity in the protein-protein interaction. The ultrafast resonance energy transfer from IAEDANS in the protein to FITC also revealed different dynamic flexibility in the allosteric interaction. An attempt was made to correlate the dynamic changes in the protein dimers with OE and OI with the consequent protein-protein interaction (tetramerisation) to form a DNA loop encompassing the promoter segment.
authors.affiliation: Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata, 700 098, India.
authors.forename: Susobhan
authors.initials: S
authors.lastname: Choudhury
authors.affiliation: Division of Structural Biology and Bioinformatics, Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Kolkata, 700 032, India.
authors.forename: Gitashri
authors.initials: G
authors.lastname: Naiya
authors.affiliation: Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata, 700 098, India.
authors.forename: Priya
authors.initials: P
authors.lastname: Singh
authors.affiliation: Institute for Condensed Matter Physics and Laboratory for Emerging Nanometrology, TU Braunschweig, Mendelssohnstrasse 3, 38106, Braunschweig, Germany. p.Lemmens@tu-bs.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Lemmens
authors.affiliation: Division of Structural Biology and Bioinformatics, Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Kolkata, 700 032, India.
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Roy
authors.affiliation: Department of Chemical, Biological & Macromolecular Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector III, Salt Lake, Kolkata, 700 098, India. skpal@bose.res.in.
authors.forename: Samir Kumar
authors.initials: SK
authors.lastname: Pal
mesh_terms: D000494:Allosteric Regulation; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D016231:Fluorescence Polarization Immunoassay; D031541:Fluorescence Resonance Energy Transfer; D008954:Models, Biological; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012097:Repressor Proteins / Q000737:chemistry*; D013997:Time Factors
chemical_list: D029968:Escherichia coli Proteins; C050993:Galactose repressor proteins; D012097:Repressor Proteins; D004247:DNA
keywords: FRET; allostery; conformational dynamics; gene expression; operator DNA; protein structures