Tsui, Hui Su (Sue)

Sue is a student in the Biochemistry, Molecular and Structural Biology Graduate Program, where she works in the laboratory of Dr. Cathy Clarke.  She joined the CMB training program in 2016.  She received a B.S. and M.S. degree in 2013 from the University of California, Los Angeles.

Mentor: Dr. Cathy Clarke

Research project:

Coenzyme Q (ubiquinone or Q) functions as an essential redox-active lipid in respiratory electron and proton transport in cellular energy metabolism, and it is an important lipid-soluble antioxidant in cellular membranes. In Saccharomyces cerevisiae, many of the Coq polypeptides responsible for Q biosynthesis assemble into a high molecular weight, multi-subunit complex localized to the matrix side of the mitochondrial inner membrane. Absence of these Coq polypeptides abolishes Q biosynthesis, and the corresponding null mutants are unable to respire. My research involves characterization of Coq10, a putative steroidogenic acute regulatory-related lipid transfer (StART) domain protein in S. cerevisiae. Unlike other Q-less coq deletion mutants, yeast coq10 null mutants contain near wild-type steady-state levels of Q6, but are nonetheless respiratory deficient. The structure of CC1736, a homolog of Coq10 in Caulobacter crescentus, contains a hydrophobic tunnel characteristic of StART domain proteins. Purified CC1736 is capable of binding Q and a farnesylated analog of a late-stage Q biosynthetic intermediate. These observations suggest Coq10 may be necessary for Q function in respiratory electron transport. Coq10 is speculated to be a Q-binding protein interacting with the multi-subunit Coq polypeptide complex and facilitating final delivery of Q from its site of synthesis to respiratory electron transport chain complexes. I will isolate and characterize the high molecular weight Coq10 oligomer using coimmunoprecipitation and mass spectrometry-based proteomic analysis. The protein partners identified through this approach will provide important clues about the molecules required for Coq10 function.