Oxidation reduction properties of thioredoxin and related proteins
Setterdahl, Aaron Tait
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Thioredoxins are redox-active proteins that contain two cysteines separated by two amino acids. These cysteines form an intreimolecular disulfide bond which when reduced, can activate or inactivate a number of other redox-sensitive proteins. This dissertation focuses on thiol-containing proteins that are involved in redoxsensitive dithiol/disulfide processes. Escherichia coli thioredoxin is a widely studied protein. However, much remains to be learned about the mechanism by which it reduces target proteins. An investigation of redox properties of the wild-type protein and site-specific mutants has been undertaken. Thioredoxin h from the green alga Chlamydomonas reinhardtii is a structurally similar protein to E. coli thioredoxin and its redox properties have also been investigated. The ligation of the heme group in cytochrome c involves a dithioydisulfide protein cascade. HelX and Ccl2 are involved in this cascade in Rhodobacter capsulatus, ultimately reducing the disulfide on apo-cytochrome c so that it can bind heme. DisuMde/dithiol systems are also involved in the oxygen sensing mechanism of Rb. capsulatus, where the DNA-binding protein CrtJ contains a redox-active disulfide. Other proteins investigated for their disulfide/dithiol activity include an engineered E. coli malate dehydrogenase, in which a redox-active disulfide was introduced, and APS reductase from Arabidopsis thaliana, which contains a redox-active regulatory disulfide.