title: DNA binding ability of histone-like protein HPhA is negatively affected by interaction with Pb2+.
abstract: The histone-like protein (HPhA) is highly homologous to the eukaryotic histones and has the ability to bind to the DNA molecules. In this study, we tested divalent metal ions Mg(2+), Ca(2+), Zn(2+), Pb(2+) for their effect on the recombinant HPhA (rHPhA)-DNA binding. We found that only Pb(2+) was able to reduce the formation of rHPhA-DNA complex using gel mobility shift assays. Equilibrium dialysis showed that Pb(2+) bound to rHPhA by a 2:1 ratio. The interaction of Pb(2+) and rHPhA was further studied by spectroscopic method including fluorescence, ultraviolet visible (UV-Vis) absorption, and circular dichroism (CD) spectroscopies. Fluorescent spectroscopy results suggested that Pb(2+) and rHPhA formed a complex that caused internal quenching of the fluorescence of the protein at the ground state, and the quenching is predominately static and mixed with dynamic quenching. UV-Vis absorption spectrum results showed Pb(2+) caused a slightly blue shift of the maximum absorption wavelength of rHPhA which indicated the reduction of the protein's hydrophobicity. The CD spectrum further indicated that a reduction of the α-helix content of rHPhA occurred upon binding to Pb(2+). Synchronous fluorescence spectrometry analysis revealed that Pb(2+) was able to affect the polarity of the amino acids that near the Trp and Tyr residues. These results together showed that Pb(2+) interact with the recombinant rHPhA and this interaction negatively affect the ability of rHPhA to form complex with DNA molecules.
authors.affiliation: Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, College of Life Science, Jilin University, 2699 Qianjin Street, Changchun, 130012, People's Republic of China.
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Wang
authors.forename: Ye
authors.initials: Y
authors.lastname: Wang
authors.forename: Yang
authors.initials: Y
authors.lastname: Zhan
authors.forename: Jinrui
authors.initials: J
authors.lastname: Zhang
authors.forename: Weiguo
authors.initials: W
authors.lastname: Liang
authors.forename: Xuexun
authors.initials: X
authors.lastname: Fang
authors.forename: Dahai
authors.initials: D
authors.lastname: Yu
authors.forename: Yan
authors.initials: Y
authors.lastname: Feng
mesh_terms: D002942:Circular Dichroism; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D007854:Lead / Q000378:metabolism*; D011485:Protein Binding; D013050:Spectrometry, Fluorescence
chemical_list: D004268:DNA-Binding Proteins; D007854:Lead; D004247:DNA