Measurement of side-chain carboxyl pK(a) values of glutamate and aspartate residues i
 

Measurement of side-chain carboxyl pK(a) values of glutamate and aspartate residues in an unfolded protein by multinuclear NMR spectroscopy.

Related Articles Measurement of side-chain carboxyl pK(a) values of glutamate and aspartate residues in an unfolded protein by multinuclear NMR spectroscopy.

J Am Chem Soc. 2002 May 22;124(20):5714-7

Authors: Tollinger M, Forman-Kay JD, Kay LE

A triple-resonance NMR pulse scheme is presented for measuring aspartic and glutamic acid side-chain pK(a) values in unfolded protein states where chemical shift overlap is limiting. The experiment correlates side-chain carboxyl carbon chemical shifts of these residues with the backbone amide proton chemical shift of the following residue. The methodology is applied to an (15)N, (13)C labeled sample of the N-terminal SH3 domain of the Drosophila protein drk, which exists in equilibrium between folded (F(exch)) and unfolded (U(exch)) states under nondenaturing conditions. Residue-specific pK(a) values of side-chain carboxyl groups are presented for the first time for an unfolded protein (drk U(exch) state), determined from a pH titration. Results indicate that deviations from pK(a) values measured for model compounds are likely due to local effects, while long-range electrostatic interactions appear to be of minor importance for this protein.

PMID: 12010044 [PubMed - indexed for MEDLINE]



Source: PubMed