title: Molecular modeling of RecX reveals its mode of interaction with RecA.
abstract: The protein RecA is involved in homologous recombination, DNA repair and also catalyzes DNA strand exchange. RecX gene is downstream of recA and the gene product RecX is supposed to be important for RecA regulation. Recombinant RecX is purified to homogeneity, and circular dichroism (CD) and FTIR spectroscopy show the protein to exist mostly in helical conformation. The fluorescence emission maxima of the native and the denatured protein and the steady-state fluorescence quenching studies with acrylamide indicate the presence of tryptophan residues partially exposed to the bulk solvent. Denaturation studies with urea and guanidine hydrochloride by use of spectroscopic methods, fluorescence, and CD also confirm the instability of the protein and unfolding occurs following a two-state model. Mass spectrometry and gel permeation chromatography suggest the monomeric form of the protein. Molecular modeling of RecX represents the molecule as extended and helical bundle in conformity with the spectroscopic results. To understand the mechanism of RecX in the regulation of RecA the structural model of RecA-RecX has been discussed. In this proposed model, entry of RecX into hexameric RecA filament prevents binding of ssDNA and also inhibits ATPase activity.
authors.affiliation: Department of Biotechnology, Indian Institute of Technology, Kharagpur 721302, India.
authors.forename: Subhra
authors.initials: S
authors.lastname: Mishra
authors.forename: Pooja Anjali
authors.initials: PA
authors.lastname: Mazumdar
authors.forename: Joykrishna
authors.initials: J
authors.lastname: Dey
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Das
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D002942:Circular Dichroism; D003198:Computer Simulation; D017124:Conserved Sequence; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D011938:Rec A Recombinases / Q000737:chemistry* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C531244:RecX protein, E coli; C430523:RecX protein, Xanthomonas campestris; D011994:Recombinant Proteins; D011938:Rec A Recombinases