Water solubilization of membrane proteins. Extensive derivatization with a novel polar derivatizing reagent.

A reagent and a derivatization procedure have been developed which result in trimesylation of all -OH and -NH2 groups on proteins: serine, threonine, tyrosine, and lysine side chains are all completely derivatized. The parameters affecting the kinetics of trimesylation of serine, threonine, and tyrosine peptides were studied using dinitrophenylated peptides as model systems. Conditions for solubilization of proteins in anhydrous organic solvents for the derivatization are described; removal of blocking groups results in the polar, highly water-soluble protein derivative which behaves as a monomer during gel permeation chromatography in simple aqueous buffers even in the absence of detergents. Synthesis of the tritiated reagent is described, and this reagent was used to monitor the protein derivatization.