Site-Specific Reactivities of Cysteine Residues in Horse L-Apoferritin

Abstract

Recombinant horse L-apoferritin and its mutants were used to compare the reactivities of two different cysteinyl residues with 7-fluoro-4-sulfamoyl-2,1,3-benzoxadiazole (ABD-F), p-chloromercuribenzoic acid (PCMB), N-(9-acridinyl)maleimide (NAM), and 4-maleimido-2,2,6,6-tetramethylpiperidine-N-oxyl (NEM-TEMPO). ABD-F selectively reacted with cysteine 52 (C52), which is located on the inner surface of the peptide shell of apoferritin. In contrast, PCMB reacted only with cysteine 130 (C130), which is located at the 3-fold channels of the shell. NAM and NEM-TEMPO reacted with both C52 and C130.