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The Skaggs Institute
for Chemical Biology
Structure and Biology of Multidrug Transporters
G. Chang, S. Aller, Y. Chen, X. He, A. Karyakin, S. Lieu, T. Nguyen, M. Revin,
P. Szewczyk, A. Ward, J. Yu
Determining
the x-ray structures of multidrug resistance (MDR) transporters is important for
the development of future antibiotics. We are interested in the structural basis
for the transport of drugs and lipids across the cell membrane by bacterial and
mammalian MDR transporters. We use several techniques, including detergent/lipid
protein chromatography, crystallization of membrane proteins, and protein x-ray
crystallography. Our experimental strategies include the overexpression, purification,
and 3-dimensional crystallization of these integral membrane proteins.
We
have determined the structures of several conformations of the lipid flippase MsbA.
MsbA is a bacterial homolog of human P-glycoprotein, which causes MDR in the treatment
of cancer. In collaboration with R. Milligan, Scripps Research, we are using electron
cryomicroscopy to study other conformations. In collaboration with M.G. Finn, the
Skaggs Institute, and Q. Zhang, Scripps Research, we are designing novel inhibitors.
We have also determined the x-ray structures of proton-drug antiporters, including
EmrE from the small multidrug transporter family and EmrD from the major facilitator
superfamily. We are also working to solve the structures of other bacterial MDR
transporters, including those from the multiple antimicrobial toxin extrusion family.
Through the
support of the Skaggs Institute, we have expanded our crystallography efforts to
include mammalian MDR transporters such as P-glycoprotein that confer resistance
in the treatment of several cancers. A single P-glycoprotein molecule contains 2
intracellular nucleotide-binding domains and 2 transmembrane-spanning domains and
is independently capable of transporting substrates as a monomer. We recently obtained
3-dimensional crystals of P-glycoprotein and are determining its x-ray structure
to facilitate the chemical design of new MDR inhibitors.
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