Alejandro P. Heuck
Associate Professor of Biochemistry and Molecular Biology, University of Massachusetts
Ph.D. : University of Buenos Aires, Argentina Postdoctoral training : Texas A&M University
Engineering bacterial toxin to measure cholesterol levels in cell membranes Some bacterial protein toxins function by binding to the surface of mammalian cells, inserting into the bilayer, and creating holes in the membrane that lead to cell death. Perfringolysin O (PFO) is secreted by Clostridium perfringens, the pathogenic bacteria that cause gas gangrene. PFO binds to cholesterol-containing membranes and oligomerizes to form large pores with diameters of ~300 Å. The C-terminus of PFO (domain 4) mediates its initial binding to the membrane, and this binding trigger the structural rearrangements required to initiate the oligomerization of PFO monomers. Our goal is to develop molecular probes that will ultimately allow the quantification and imaging of distinct cholesterol levels in cell membranes. Assembly of the Type III secretion translocon in membranes Several pathogenic bacteria including Yersina ssp., Salmonella ssp., enterophatogenic E. coli, Pseudomonas aeruginosa, Shigella flexneri, etc., inject proteins directly into the eukaryotic cell cytoplasm to interfere with and to alter host processes. These proteins are presumably injected through the eukaryotic cell membrane via a proteinaceous transmembrane channel known as translocon, which is of bacterial origin. The translocons are thought to be transmembrane protein complexes consisting of several components. Our goal is to understand, at a molecular level, the assembly mechanism of the Type III secretion translocon into the target cell membrane. We employ a variety of biophysical, biochemical, and molecular biological approaches to study protein structure, protein-membrane and protein-protein interactions.