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.
Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Cheryl A
CA
Blasie
Jeremy M
JM
Berg
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