Crystallographic Studies of Iron Proteins

Citation

Yeh, Andrew Peter (2002) Crystallographic Studies of Iron Proteins. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/25dt-ct33. https://resolver.caltech.edu/CaltechTHESIS:02072012-093202232

Abstract

The crystal structures of a number of iron proteins from various microbes have been determined in order to better understand the structure-function relationship of these proteins. Several of these iron proteins are as follows:

Superoxide Reductase (SOR) from the hyperthermophile Pyrococcus furiosus. SOR is a non-heme mono-iron protein that functions in anaerobic microbes (e.g., Pyrococcus furiosus) as a defense mechanism against reactive oxygen species by catalyzing the reduction of superoxide to hydrogen peroxide. Crystal structures of SOR in both its oxidized and reduced states have been determined and suggest a possible mechanism by which superoxide accessibility may be regulated.

[2Fe-2S] Ferredoxin 4 (Fd4) from the hyperthermophile Aquifex aeolicus. The crystal structure of this [2Fe-2S] ferredoxin has been determined and reveals a thioredoxin-like fold that is novel among iron-sulfur proteins. Protein sequence alignments show that this fold is present as components of more complex anaerobic and aerobic electron transfer systems (e.g., complex I of aerobic respiratory chains). The crystal structures of two variants of this protein in which one of the [2Fe-2S] cysteine ligands was substituted with a serine have also been determined. The structures of these variants provide metric details of unprecedented accuracy for serine-ligated iron-sulfur clusters in proteins.

The Photosynthetic Reaction Center (RC) from the photosynthetic purple bacterium Rhodobacter sphaeroides. The plimary process of bacterial photosynthesis, which is light-induced trans-membrane charge separation, occurs in the reaction center (RC), an integral membrane protein-pigment complex. We have obtained the crystal structures of the RC bound to the inhibitor stigmatellin in the presence and absence of light to determine any structural change(s) that may be associated with one of its light-induced charge-separated (D^+QA^-) states. In addition, we have determined the crystal structure of the RC complexed with its physiological electron donor, the soluble monoheme protein cytochrome C_2.

Thesis Files