Erwin London

Title: Membrane Protein Structure: Determining the Rules for Membrane Protein Translocation and Folding.

Our group is studying membrane protein structure and function by combining spectroscopic methods, such as fluorescence, with chemical, biochemical, immunochemical and molecular biological approaches. We are interested in the determining membrane protein structure and the origin of specific lipid-protein and protein-protein interactions. At present, we are concentrating on protein toxins that penetrate and translocate across cell membranes, such as diphtheria toxin. Our aim is to understand the mechanism of membrane penetration and traslocation by this toxin. This should have important implications for protein translocation in general, as well as the design of therapeutic agents and vaccines for bacterial infections. One specific technique we are developing involves using antibody binding to study structure. Another involves the determination of the depth of groups by a fluorescence quenching technique. These methods are being combined with site-directed mutagenesis in order to define the structure of the toxin in its membrane-nserted state. We are also using fluorescence to study the relationship between amino acid sequence and structure using synthetic transmembrane helices. These studies are aimed at determining the basic rules for membrane protein folding.

Kachel, K, Asuncion-Punzalan, E. and London, E. (1995) Anchoring of tryptophan and tyrosine analogs at the hydrocarbon-polar boundary in model membrane vesicles. Parallax analysis of fluorescence quenching. Biochemistry 34:15475-15479.

Tortorella, D., Sesaric, D., Dawes, C.S., and London, E. (1995) Immunochemical analysis of the structure of diphtheria toxin. J. Biol. Chem. 270: 27439-27445.

Tortorella, D., Sesardic, D., Dawes, C.S., and London, E. (1995) Immunochemical analysis shows all three domains of diphtheria toxin penetrate across model membranes. J. Biol. Chem. 270: 27446-27452.

Paliwa, R., and London, E. (1996) Comparison of the conformation, hydrophobicity and model membrane interactions of diphtheria toxin to those of formaldehyde-treated diphtheria toxin (diptheria toxoid). Biochemistry 35, 2374-2379.

Ren, J., Lew, S., Wang.,Z., and London, E. (1997) Transmembrane orientation of hydrophobic alpha helices is regulated both by the relationship of helix length to bilyaer thickness and by cholesterol concentration. Biochemistry, in press.