positions for postdoctoral fellows
james_hogle at hms.harvard.edu
Thu Jun 3 14:47:37 PDT 2004
We have openings for one or two postdocs with experience with cryo
electron microscopy and image reconstruction methods to study the cell
entry mechanism of poliovirus and related picornaviruses.
Over the years we have solved the structure of the virus and a key
assembly intermediate at high resolution by x-ray crystallography, and
in collaboration with David Belnap and Alasdair Steven at NIH we have
solved the structures of the virus-receptor complex and of an early
cell entry intermediate at intermediate resolution (currently ~10Å) and
of the final product of the entry pathway at moderate resolution (~20Å)
by cryo electron microscopy. These structures together with ongoing
work in our laboratory and elsewhere has led to a working model for
poliovirus cell entry in which receptor mediated conformational changes
result in the exposure of hydrophobic sequences (including a small
myristylated protein VP4 and the N-terminus of the capsid protein VP1)
that are inserted in the membrane to form a channel which allows the
viral RNA genome to cross the cell membrane and enter the cytoplasm
(Hogle (2002) Ann. Rev. Microbiol. 56, 677-702).
In order to test this model, we have developed a simple liposome-based
model system that allows the efficient incorporation of receptors,
virus binding, and induces the receptor-mediated conformational changes
to produce a stable complex between the altered virus and the membrane.
We have initiated structural studies of the virus-receptor-liposome
complex with the virus and receptor on the outside of the liposome
(mimicking the initial virus cell complexes) using multiple particle
reconstruction techniques with very promising initial results. In
collaboration with the Boulder Laboratory for 3D Microscopy of Cells,
we have also initiated cryotomographic studies of the virus-receptor
liposome complexes and are working on approaches that will allow us to
average over multiple tomographic reconstructions of the complex. We
have planned parallel studies of the altered-virus-liposome complex
(with a goal of visualizing the channel), and virus-receptor-liposome
and altered virus – liposome complexes in which the virus is on the
inside of the liposome (mimicking virus in internalized vesicles).
These studies will be carried out in parallel with ongoing optical
microscopy studies in both live and fixed cells.
The lab has access to state-of-the-art microscopy (Tecnai F12, F20, and
F30 microscopes) and computational facilities.
If you are interested please send a CV and names of references to Jim
Hogle at jhogle at hms.harvard.edu.
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