TY - JOUR
T1 - Substitution of Glutamate Residue by Lysine in the Dimerization Domain Affects DNA Binding Ability of HapR by Inducing Structural Deformity in the DNA Binding Domain
AU - Singh, Richa
AU - Rathore, Yogendra Singh
AU - Singh, Naorem Santa
AU - Peddada, Nagesh
AU - Ashish,
AU - Raychaudhuri, Saumya
N1 - Funding Information:
We thank the Director of Institute of Microbial Technology (IMTECH), Council of Scientific and Industrial Research (CSIR), India, to support our research pursuits. Use of the National Synchrotron Light Source, Brookhaven National Laboratory, was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. We gratefully acknowledge Dr. Giesla Storz, National Institute of Health, Bethasda, MA, U.S.A. for providing the pKK177-3RI plasmid and Dr. Jun Zhu, University of Pennsylvania School of Medicine, Philadelphia PA, USA for critical suggestions.
PY - 2013/10/14
Y1 - 2013/10/14
N2 - HapR has been given the status of a high cell density master regulatory protein in Vibrio cholerae. Though many facts are known regarding its structural and functional aspects, much still can be learnt from natural variants of the wild type protein. This work aims at investigating the nature of functional inertness of a HapR natural variant harboring a substitution of a conserved glutamate residue at position 117 which participates in forming a salt bridge by lysine (HapRV2G-E117K). Experimental evidence presented here reveals the inability of this variant to interact with various cognate promoters by in vitro gel shift assay. Furthermore, the elution profiles of HapRV2G-E117K protein along with the wild type functional HapRV2G in size-exclusion chromatography as well as circular dichroism spectra did not reflect any significant differences in its structure, thereby indicating the intactness of dimer in the variant protein. To gain further insight into the global shape of the proteins, small angle X-ray scattering analysis (SAXS) was performed. Intriguingly, increased radius of gyration of HapRV2G-E117K of 27.5 Å in comparison to the wild type protein from SAXS data analyses implied a significant alteration in the global shape of the dimeric HapRV2G-E117K protein. Structure reconstruction brought forth that the DNA binding domains were substantially "parted away" in this variant. Taken together, our data illustrates that substitution of the conserved glutamate residue by lysine in the dimerization domain induces separation of the two DNA binding domains from their native-like positioning without altering the dimeric status of HapR variant.
AB - HapR has been given the status of a high cell density master regulatory protein in Vibrio cholerae. Though many facts are known regarding its structural and functional aspects, much still can be learnt from natural variants of the wild type protein. This work aims at investigating the nature of functional inertness of a HapR natural variant harboring a substitution of a conserved glutamate residue at position 117 which participates in forming a salt bridge by lysine (HapRV2G-E117K). Experimental evidence presented here reveals the inability of this variant to interact with various cognate promoters by in vitro gel shift assay. Furthermore, the elution profiles of HapRV2G-E117K protein along with the wild type functional HapRV2G in size-exclusion chromatography as well as circular dichroism spectra did not reflect any significant differences in its structure, thereby indicating the intactness of dimer in the variant protein. To gain further insight into the global shape of the proteins, small angle X-ray scattering analysis (SAXS) was performed. Intriguingly, increased radius of gyration of HapRV2G-E117K of 27.5 Å in comparison to the wild type protein from SAXS data analyses implied a significant alteration in the global shape of the dimeric HapRV2G-E117K protein. Structure reconstruction brought forth that the DNA binding domains were substantially "parted away" in this variant. Taken together, our data illustrates that substitution of the conserved glutamate residue by lysine in the dimerization domain induces separation of the two DNA binding domains from their native-like positioning without altering the dimeric status of HapR variant.
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U2 - 10.1371/journal.pone.0076033
DO - 10.1371/journal.pone.0076033
M3 - Article
C2 - 24155884
AN - SCOPUS:84885397058
SN - 1932-6203
VL - 8
JO - PloS one
JF - PloS one
IS - 10
M1 - e76033
ER -