S-nitrosylation (or S-nitrosation) has emerged as an important pathway of non-classical nitric oxide signaling. This post-translational modification involves the transfer of a nitroso group onto a cysteine residue and has been shown to regulate protein function. However, very little is known about the mechanism and structure-dependent factors of the modification. Understanding of S-nitrosothiol chemistry has lagged behind that for the classical nitric oxide signaling pathway due to challenges and limitations of current detection methods of S-nitrosothiols. The S-N bond is typically labile and indirect detection by traditional biotin switch method has low sensitivity and is prone to false positives. In this work, I have explored phosphine derivatization as a new direct approach to labeling protein S-nitrosothiols. Syntheses of aza-ylide derivatives of small organic S-nitrosothiols were successful and the termolecularity of the reaction was overcome by using a bisphosphine. Similarly, S-nitrosated cysteines of thioredoxin were successfully derivatized with the phosphine TCEP and identified by tandem mass spectrometry of the digested protein. Surprisingly, derivatization of S-nitrosoglutathione was found to be unsuccessful and ¹⁸O-labeling of the reaction indicated hydrolysis of the aza-ylide product. We hypothesize that solvent effects are the source of this discrepancy. In addition, x-ray crystallography studies were undertaken to investigate structural rearrangement of a thioredoxin helix to expose residue Cys 62 to S-nitrosation. A new structure of thioredoxin Q63A/C69S/C73S mutant was found to exhibit a highly dynamic N-terminal loop surrounding the pocket of Cys 62 which could have an effect on S-nitrosation of this residue.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/312667 |
| Date | January 2013 |
| Creators | The, Juliana |
| Contributors | Montfort, William R., Montfort, William R., Glass, Richard S., Cordes, Matthew H. J., Miesfeld, Roger L. |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | en_US |
| Detected Language | English |
| Type | text, Electronic Dissertation |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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