I gained an early interest in proteins and the role of hydrophobic forces in protein folding
as an undergraduate at Princeton University working in Professor Walter Kauzmann’s
lab. I continued my interest in proteins while a graduate student in Professor Esmond
Snell’s group at the University of California and was later attracted to Professor Eugene
Kennedy’s lab as a postdoctoral fellow at Harvard Medical School based on his initial
detection of the membrane associated M protein, which is the lactose permease (LacY)
of Escherichia coli. After my failure to purify LacY, I turned to successfully isolating
membrane-associated enzymes of phospholipid biosynthesis for the remainder of my
postdoctoral fellowship and in the early years as an assistant professor at the University
of Texas Medical School at Houston. Therefore, I acquired expertise and interest in the
two major components of membranes, lipids and proteins, where a strong grounding in
the principles of the hydrophobic effect became important. In 1985 I took a sabbatical
leave in the laboratory of Professor Gottfried Schatz in Basel, Switzerland. Here I was
introduced to mitochondrial biochemistry and genetics in Saccharomyces cerevisiae.
This experience resulted in a major shift in my research direct by incorporating yeast
genetics and studies of mitochondrial function into my research program. Most important
was learning the ease and power of complete gene knockouts in yeast as a means of
gaining clues to function. I was intrigued with the developing power of molecular
genetics and began cloning genes and constructing mutants involved in phospholipid
metabolism in yeast and E. coli in order to gain insight into functions of lipids in cells
other than membrane bilayer formation. These studies led to the construction of mutants
in which membrane phospholipid synthesis could be systematically regulated in a dosedependent manner at steady state and temporally during the cell cycle. The result was a
set of viable microorganisms that display a spectrum of phenotypes related to the
requirement for specific phospholipids. I came full circle back to studies of LacY in 1992
because elimination of phosphatidylethanolamine in E. coli results in a functional
defective in LacY and other related secondary transporters. The biochemical dissection
of the molecular basis for the defect in LacY function led Dr. Mikhail Bogdanov and me
over the following years and Dr. Heidi Vitrac in recent years to define specific roles for
membrane lipids as determinants of membrane protein topological organization in E.
coli. The development of mutants in mitochondrial phospholipid synthesis formed the
basis for Dr. Eugenia Mileykovskaya and me to understand the critical role of cardiolipin
in the organization and function of the mitochondrial respiratory chain. As a result, a
continuing interest of mine is to use a combination of biochemical, genetic and structural
approaches to undercover and define novel roles for lipids in cell function, which will now
be extended to more complex eukaryotic systems.