The Selective S-Methylation of Sulfhydryl Groups in Proteins and Peptides with Methyl-p-nitrobenzenesulfonate
Year: 1971
Type: article
Abstract: The cysteine residues in proteins and peptides may be quantitatively and selectively converted to the S-methyl derivatives by reaction with methyl-p-nitrobenzenesulfonate. Procedures are described for the reduction and methylation of a variety of proteins at pH 8.6 and 37°, together with the pH rate profile for the methylation of reduced glutathione at 25°. The methylation of S-sulfoinsulin B chain and an S-benzylcysteinyl pentapeptide was performed after removal of the protective groups by mercaptoethanol and sodium in liquid ammonia, respectively. Amino acid analysis of the various S-methylated proteins and peptides revealed no modifications other than the quantitative conversion of cysteine to S-methylcysteine. The specific radioactivity and amino acid analysis of 14C-methylcysteinyl rhodanese isolated after reaction with radioactive reagent revealed that the modifications were confined to the 2 cysteine residues in rhodanese monomer. Methylation of the presumed active site cysteine residue in papain occurred only in 7 m urea and was accompanied by inactivation of the enzyme; papain was refractive to the reagent in the absence of denaturing agents.
Source: Journal of Biological Chemistry
Author: Robert L. Heinrikson
Institution: University of Chicago
Language: English
Topic: Sulfur Compounds in Biology
Subfield: Biochemistry
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1552944091