A Kinetic Approach to Characterize the Electrostatic Environments of Thiol Groups in Proteins

✍ Scribed by Hao Zhang; Min Le; Gary E. Means

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 226 KB
• Volume: 26
• Category: Article
• ISSN: 0045-2068
• DOI: 10.1006/bioo.1998.1112

✦ Synopsis

In this study, we synthesized a zwitterionic DTNB derivative, 5-(2-aminoethyl)-dithio-2nitrobenzoate (ADNB), and characterized its reactions with several cationic, anionic, and neutral thiols. Reactions with ADNB, unlike those with DTNB, are relatively insensitive to electrostatic environments and ionic strengths. At relatively low ionic strength, rate ratios, k ADNB /k DTNB , varied from 0.22 for reactions with low-molecular-weight cationic thiols to 3.0 for those with low-molecular-weight anionic thiols. A k ADNB /k DTNB ratio of ȁ200 for Cys-34 of BSA appears to reflect a very anionic environment. k ADNB /k DTNB ratios of ȁ6 and ȁ1, respectively, for canine and equine serum albumins, which have Glu-82 Ǟ Asp and Glu-82 Ǟ Ala substitutions suggest Glu-82 is the most important anionic residues affecting the reactivity of Cys-34 in BSA. k ADNB /k DTNB ratios appear to be useful for characterizing electrostatic environments of thiol groups in proteins.