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Alejandro P. Heuck

Associate Professor


LGRT 1228
(413) 545-2497


Pore-forming toxins and translocation of virulence factors in bacterial pathogenesis

Background and Training

PhD: University of Buenos Aires, Argentina
Postdoctoral training: Texas A&M University, College of Medicine

Research Summary

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.


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 [Biochemistry online]

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 [PubMed]

Romano F. B.,; Rossi, K.; Sava, C.G.; Holzenburg, A.; Clerico, E.M.; Heuck A. P. Efficient isolation of Pseudomonas aeruginosa type III secretion translocators and assembly of heteromeric transmembrane pores in model membranes. Biochemistry 2011. 50 (33), pp 7117–7131. [PubMed]

Raghava S., Giorda K. M., Romano F. B., Heuck A. P., & Hebert D. N. The SV40 late protein VP4 is a viroporin that forms pores to disrupt membranes for viral release. PLoS Pathogens 2011. 7 (6), e1002116. [PubMed]

Moe P.C. & Heuck A.P. Phospholipid Hydrolysis Caused by Clostridium perfringens alpha-toxin Facilitates the Targeting of Perfringolysin O to Membrane Bilayers. Biochemistry 2010 49 (44) pp 9498-9507. [PubMed]

Flanagan J.J., Tweten R.K., Johnson A.E., Heuck A.P. Cholesterol Exposure at the Membrane Surface Is Necessary and Sufficient to Trigger Perfringolysin O Binding. Biochemistry 2009 48(18):3977-87. [PubMed]