Arginine: Its PKa Value Revisited

Overview

Journal Protein Sci

Specialty Biochemistry

Date 2015 Mar 27

PMID 25808204

Citations 119

Authors

Carolyn A Fitch

Gerald Platzer

Mark Okon

Bertrand E Garcia-Moreno

Lawrence P McIntosh

Affiliations

Soon will be listed here.

Abstract

Using complementary approaches of potentiometry and NMR spectroscopy, we have determined that the equilibrium acid dissociation constant (pKa value) of the arginine guanidinium group is 13.8 ± 0.1. This is substantially higher than that of ∼ 12 often used in structure-based electrostatics calculations and cited in biochemistry textbooks. The revised intrinsic pKa value helps explains why arginine side chains in proteins are always predominantly charged, even at pH values as great as 10. The high pKa value also reinforces the observation that arginine side chains are invariably protonated under physiological conditions of near neutral pH. This occurs even when the guanidinium moiety is buried in a hydrophobic micro-environment, such as that inside a protein or a lipid membrane, thought to be incompatible with the presence of a charged group.

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