Cysteine 904 Is Required for Maximal Insulin Degrading Enzyme Activity and Polyanion Activation |
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| Authors: | Eun Suk Song Manana Melikishvili Michael G. Fried Maria A. Juliano Luiz Juliano David W. Rodgers Louis B. Hersh |
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| Affiliation: | 1. Department of Molecular and Cellular Biochemistry and the Center for Structural Biology, University of Kentucky, Lexington, Kentucky, United States of America.; 2. Department of Biophysics, Universidade Federal de Sao Paulo, Escola Paulista de Medicina, Rua Tres de Maio, Sao Paulo, Brazil.; Omaha Veterans Affairs Medical Center, United States of America, |
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| Abstract: | Cysteine residues in insulin degrading enzyme have been reported as non-critical for its activity. We found that converting the twelve cysteine residues in rat insulin degrading enzyme (IDE) to serines resulted in a cysteine-free form of the enzyme with reduced activity and decreased activation by polyanions. Mutation of each cysteine residue individually revealed cysteine 904 as the key residue required for maximal activity and polyanion activation, although other cysteines affect polyanion binding to a lesser extent. Based on the structure of IDE, Asn 575 was identified as a potential hydrogen bond partner for Cys904 and mutation of this residue also reduced activity and decreased polyanion activation. The oligomerization state of IDE did not correlate with its activity, with the dimer being the predominant form in all the samples examined. These data suggest that there are several conformational states of the dimer that affect activity and polyanion activation. |
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