Advisor
Yana S. Bukhman-DeRuyter
Ph.D. candidate (IV)
B.Sc. (Honors), Brock University (Canada), Chemistry, 2003
Ph.D. candidate (IV)
B.Sc. (Honors), Brock University (Canada), Chemistry, 2003
| Home Department | Chemistry and Biochemistry |
| Areas of Study | Crystallization of the Plastocyanin-Photosystem I supercomplex from the cyanobacterium Phormidium laminosum. |
Background Harnessing and conversion of light energy to usable chemical energy takes place in the thylakoid membranes of bacterial or plant cells via photosynthesis. During this process, light is absorbed by chlorophyll molecules in membrane-bound Photosystem II (PSII) and Photosystem I (PSI) reaction centre proteins. Subsequent events produce a unidirectional flow of electrons between reaction centers and other associated proteins, which eventually leads to the synthesis of higher organic compounds within the living organism. Cytochrome b6/f (Cytb6/f) is also a membrane protein, and acts as an intermediary in the electron transfer process. It is located in the membrane between PSII and PSI. In plants, electron transfer between Cytb6/f and PSI is mediated exclusively by Plastocyanin (PC). PC is a water-soluble, globular protein containing a copper ion. However, many algae or cyanobacteria can use either PC or Cytochrome c6 (Cytc6). Cytc6 is a heme protein containing iron instead of copper, depending on the relative availability of copper and iron in the environment. Although the structures of PC and Cytc6 are vastly different, the two are functionally equivalent. During electron transfer, both PC and Cytc6 accept an electron from Cytb6/f and, in turn, reduce PSI – forming transient complexes both with the reducing and with the oxidizing partners. The docking site for both e--transfer proteins is located at an indentation in the PSI complex, on the luminal side of the membrane, and may provide the main functional interaction site with both soluble electron carriers. However, the precise nature of the interaction and character of the binding site between PC and PSI is not yet known. Mathematically driven docking models only suggest variations in electrostatics of the docking interface between plants and cyanobacteria, but no crystal structure of a PC/PSI complex exists to date. My project focuses on an investigation of cyanobacterial PC/PSI docking, with the goal of co-crystallizing PSI isolated from Phormidium laminosum in complex with wild-type and mutant PC. P. laminosum is a moderately thermophilic cyanobacterium capable of expressing either PC or Cytc6, and is very amenable to both lab culture and lysis, and has therefore been chosen as the model system for this study. |
|
Plastocyanin (Pc) crystals from the moderately thermophilic cyanobacterium Phormidium laminosum.
Photosystem I (PSI) crystals from Phormidium laminosum.
Crystals of the PSI-Pc complex from Phormidium laminosum.
[Publication]
Fromme, P., Yu, H.Q., De Ruyter, Y.S., Jolley, C., Chauhan, D.K., Melkozernov, A., Grotjohann, I., C. R. Chim. 9(2): 188-200 (2006).