Estelle McGroarty
Professor
Asst Vice President, VP Rsrch &     Grad Studies
Ast Vice Provost, Lib Comp Tech

• B.S. 1967, Purdue University
• Ph.D. 1971, Purdue University
• Postdoctoral Associate, 1972-73, Michigan State University
• Acting Chair 1975-76, Department of Biophysics, Michigan State University

mcgroar1@msu.edu
242 Administration Bldg
Michigan State University
East Lansing, MI 48824
Office: 517-432-3773


Publication search:

Estelle McGroarty

Research Interests

Gram Negative Outer Membrane Structure
The outer membrane of the Gram negative bacteria provides a protective barrier to hydrophobic and amphophilic, deleterious compounds, including certain classes of antibiotics. A unique glycolipid, lipopolysaccharide, present on the outer surface of this membrane provides part of this protective barrier. Using various techniques, we have investigated the heterogeneity and the composition of the lipopolysaccharides present on different strains of Gram negative bacteria. We have evidence that some species synthesize two chemically distinct classes of lipopolysaccharide with different antigenic reactivity. We have begun to analyze the structural differences of these distinct classes.

Although the outer membrane is relatively impermeable to hydrophobic compounds, it allows passive transport of small hydrophilic molecules. Nutrient and waste compounds must be able to traverse the outer membrane; a class of integral membrane proteins, the porins, form water-filled channels that allow passive diffusion across this membrane. We have analyzed the structure of isolated porins and their function as diffusion channels. By inserting the proteins into artificial membranes, the diffusion of small molecules across the membranes have been measured. Our initial studies have shown that changes in environmental conditions modify the structure of the porin channel, altering its size and the stability of the open state. Our studies suggest that there may be more than one stable open conformation. Molecular modelling analyses of the crystallographically determined structure of the porin is helping us define residues within the channel which stabilize specific conformations. The involvement of such residues will be tested by site-directed mutagenesis.

---