Entropy-enthalpy compensation in ionic interactions probed in a zinc finger peptide.
Zinc(II) and cobalt(II) binding to a series of zinc finger peptides with different charged residue pairs across from one another in a beta-sheet were examined. Previous studies revealed a narrow range of interaction free energies (<0.5 kcal/mol) between these residues. Here, isothermal titration calorimetry studies were performed, revealing a range of over 3 kcal/mol in relative binding enthalpies. Double mutant cycle analysis revealed a range of interaction enthalpies ranging from -3.1 to -3.4 kcal/mol for the Arg-Asp pair to -0.8 kcal/mol for the Lys-Glu pair. The large range of interaction enthalpies coupled with the small range of interaction free energies reveals substantial entropy-enthalpy compensation. The magnitudes of the effects are consistent with the formation of a structurally rigid Arg-Asp contact ion pair but less direct and more mobile interactions involving the other combinations.
Blasie
Cheryl A
CA
Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Berg
Jeremy M
JM
D002151:Calorimetry; D003035:Cobalt / Q000737:chemistry* / Q000378:metabolism; D019277:Entropy; D008956:Models, Chemical; D009154:Mutation; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017510:Protein Folding; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism; D016335:Zinc Fingers
C106243:CP-1 peptide; D009842:Oligopeptides; D003035:Cobalt; D015032:Zinc