Alejandro P. Heuck

Associate Professor of Biochemistry and Molecular Biology, University of Massachusetts

A. Heuck Biochemistry & Molecular Biology Web Site

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.

Representative publications:

Johnson B.B., Moe P.C., Wang Y.D., Rossi K., Trigatti B.L., and Heuck A.P.  Modifications in Perfringolysin O domain 4 alter the threshold of cholesterol concentration required for binding Biochemistry 2012, 51 (16), pp 3373-3382

Luthra A., Zhu G., Desrosiers D. C., Eggers C. H., Mulay V. , Anand A., McArthur F. A., Romano F. B., Caimano M. J., Heuck A. P., Malkowski M. G. , and Radolf J.D. The transition from closed to open conformation of Treponema pallidum outer membrane-associated lipoprotein TP0453 involves membrane sensing and integration by two amphipathic helices. J. Biol. Chem. 2011. Dec 2;286(48):41656-68.

Romano F.B., Rossi K.C., Sava C.G., Holzenburg A., Clerico E.M., Heuck A.P. (2011) Efficient isolation of Pseudomonas aeruginosa type III secrertion translocators and assembly of heteromeric transmembrane pores in model membranes. Biochemistry, 50, 7117-7131.

Luthra A., Zhu G., Desrosiers D.C., Eggers C.H., Mulay V., Romano F.R., Caimano M.J., Heuck A.P., Malkowski M.G., Radolf J.D. (2011) The transition from closed to open conformation of Treponema pallidum outer membrane-associated lipoprotein TP0453 involves membrane sensing and integration by two amphipathic helices. 2011 Journal of Biological Chemistry. 286, 41656-41668.

Raghava S., Giorda K.M., Romano F.B., Heuck A.P., Hebert, D. (2011) The SV40 late protein VP4 is a viroporin that forms pores to disrupt membranes for viral release. PLoS Pathogens, 7, e1002116.

Moe P.C., Heuck A.P. (2010) Phospholipid Hydrolysis Caused by Clostridium perfringens a-toxin Facilitates the Targeting of Perfringolysin O to Membrane Bilayers. Biochemistry, 49, 9498-9507.

Heuck A.P., Moe, P.C., Johnson B.B. (2010) "The cholester-dependent cytolysins family of Gram-positive bacterial toxins" in Cholesterol-binding and Cholesterol Transport Proteins: Stucture and Function in Health and Disease. Subcellular Biochemistry Series, Vol. 51, Chapter 20, 551-577. Edited by Harris R. Springer.

Flanagan J.J., Tweten R.K., Johnson A.E., Heuck A.P. (2009) Cholesterol Exposure at the Membrane Surface is Necessary and Sufficient to Trigger Perfringolysin O Binding. Biochemistry, 48, 3977-3987.