Open AccessSalt bridge dynamics in protein/DNA recognition: a comparative analysis of Elk1 and ETV6
Author(s) -
Thi-Dieu-Hien Vo,
Amelia L. Schneider,
A. Paul,
Gregory M.K. Poon
Publication year - 2021
Publication title -
physical chemistry chemical physics/pccp. physical chemistry chemical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.053
H-Index - 239
eISSN - 1463-9084
pISSN - 1463-9076
DOI - 10.1039/d1cp01568k
Subject(s) - dna , biophysics , chemistry , encode , ionic bonding , salt bridge , amino acid , computational biology , genetics , biology , biochemistry , gene , ion , organic chemistry , mutant
Electrostatic protein/DNA interactions arise from the neutralization of the DNA phosphodiester backbone as well as coupled exchanges by charged protein residues as salt bridges or with mobile ions. Much focus has been and continues to be paid to interfacial ion pairs with DNA. The role of extra-interfacial ionic interactions, particularly as dynamic drivers of DNA sequence selectivity, remain poorly known. The ETS family of transcription factors represents an attractive model for addressing this knowledge gap given their diverse ionic composition in primary structures that fold to a tightly conserved DNA-binding motif. To probe the importance of extra-interfacial salt bridges in DNA recognition, we compared the salt-dependent binding by Elk1 with ETV6, two ETS homologs differing markedly in ionic composition. While both proteins exhibit salt-dependent binding with cognate DNA that corresponds to interfacial phosphate contacts, their nonspecific binding diverges from cognate binding as well as each other. Molecular dynamics simulations in explicit solvent, which generated ionic interactions in agreement with the experimental binding data, revealed distinct salt-bridge dynamics in the nonspecific complexes formed by the two proteins. Impaired DNA contact by ETV6 resulted in fewer backbone contacts in the nonspecific complex, while Elk1 exhibited a redistribution of extra-interfacial salt bridges via residues that are non-conserved between the two ETS relatives. Thus, primary structure variation in ionic residues can encode highly differentiated specificity mechanisms in a highly conserved DNA-binding motif.