Dr. Patrice Hamel, associate professor, Department of Molecular Genetics, Ohio State University, will present the seminar "Novel Redox Enzymes in the Thylakoid Lumen" on Tues. Dec. 10, 2013 at 4:00 PM in N172 Beadle.
In the bacterial periplasm, sulfhydryl oxidation and disulfide reduction in target proteins are under the control of dedicated catalysts. The occurrence of proteins requiring free sulfhydryls or containing disulfide bonds in the thylakoid lumen, a compartment topologically related to the bacterial periplasm, suggests thiol/disulfide chemistry is also enzymatically assisted in the lumen. In the plant Arabidopsis thaliana, we have identified LTO1 (Lumen Thiol Oxidase 1), a novel sulfhydryl oxidase at the thylakoid membrane, whose activity is required for the assembly of photosystem II. PsbO, a disulfide bonded subunit of PSII in the thylakoid lumen has been identified as a relevant target of LTO1 sulfhydryl oxidase activity. In the green alga Chlamydomonas reinhardtii, CCS5 (Cytochrome C Synthesis 5) is a thylakoid membrane anchored protein with a lumen facing thioredoxin-like domain. We show that CCS5 is a component of a trans-thylakoid redox pathway and operates by reducing a disulfide at the CXXCH heme binding site of apocytochrome f in the cytochrome b6f complex, a biochemical requirement for the heme attachment reaction. Our results further highlight the role of thiol-disulfide chemistry as a catalyzed process in the biogenesis of the photosynthetic chain.