Charge-charge interactions are the primary determinants of the pK values of the ionizable groups in Ribonuclease T1.
Coulomb's law and a finite difference Poisson-Boltzmann based analysis are used to predict the pK values for 15 ionizable side chains (6 Asp, 6 Glu and 3 His) in ribonuclease T1. These predicted values are compared to the measured pK values to gain insight into the most important factors that influence the pK values of the ionizable groups in proteins. Charge-charge interactions are clearly the most important factor that determines the pK values of most ionizable groups in ribonuclease T1. However, pK values can be shifted by several pK units by the Born self energy associated with burying ionizable groups and by favorable intramolecular hydrogen bonding.
Pace
C Nick
CN
Department of Medical Biochemistry and Genetics and Center for Advanced Biomolecular Research, Texas A&M University, College Station, TX 77843-1114, USA. nickpace@tamu.edu
Huyghues-Despointes
Beatrice M P
BM
Briggs
James M
JM
Grimsley
Gerald R
GR
Scholtz
J Martin
JM
D007477:Ions; D006163:Ribonuclease T1 / Q000737:chemistry*; D013816:Thermodynamics
D007477:Ions; D006163:Ribonuclease T1