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Harold
P. Erickson
(Biophysics, Johns Hopkins University)
James
B. Duke Professor,
Department of Cell Biology
Programs: CMB, Molecular Biophysics
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Cytoskeleton: It is now clear that the actin and microtubule cytoskeleton originated in bacteria. Our
major research is on FtsZ, the bacterial tubulin homolog, which assembles into
a contractile ring that divides the bacterium. We have studied FtsZ assembly
in vitro, and found that it assembles into thin protofilaments. Dozens of these
protofilaments are further clustered to form the contractile Z-ring in vivo.
We have discovered, using FRAP, that the Z-ring is extremely dynamic, turning
over with a half time of 9 sec. This is faster even than microtubule dynamic
instability. The turnover is correlated with GTP hydrolysis. We have recently
demonstrated by FRET that protofilaments are turning over with the same dynamics
in vitro.
• We have recently developed two fluorescence assays for FtsZ assembly, and this
has permitted an analysis of kinetics and nucleation. We are extending this
analysis in several directions.
• We are using site directed mutagenesis to discover interaction sites. (Doesn't
the tubulin field wish they could use this powerful mutagenesis?)
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Speaking of tubulin, we have demonstrated in vitro assembly of BtubA-B, which
are bona fide tubulins in a bacterium. We are now developing fluorescence assays
for assembly and doing mutagenesis.
Our long term goals are two-fold. First, to understand the mechanism of bacterial
cell division, which is surprisingly less well understood than division of eukaryotic
cells. Second, to learn basic principles of assembly that will apply to both
FtsZ and tubulin. Many experiments that are impossible with eukaryotic tubulin
Extracellular
Matrix: A second interest of our lab is extracellular
matrix and cell adhesion, focusing now on fibronectin.
We have discovered that the FN matrix is very elastic,
with fibrils stretching up to four-fold over their
relaxed length. We have two possible mechanisms to
explain the elasticity of FN, and are currently developing
experimental tests to resolve the mechanism. We are
also studying the molecular structure of FN matrix
fibrils and the mechanism of assembly. Assembly of "super
FN" is providing important new insights. |
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E-mail
h.erickson@cellbio.duke.edu
367 Nanaline Duke Bldg., Box 3709
Duke University Medical Center
Durham, NC 27710
Telephone 919-684-6385
Fax
919-684-8090
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Selected
Publications
Complete
publications, and some e-prints (pdfs)
Osawa, M., D.E. Anderson, and H.P. Erickson. 2008. Reconstitution of contractile FtsZ rings in liposomes. Science. 320:792-4.
Erickson HP. Evolution of the cytoskeleton. Bioessays
2007;29(7):668-677.
Ohashi T, Galiacy SD, Briscoe G, Erickson HP. An experimental
study of GFP-based FRET, with application to intrinsically
unstructured proteins. Protein Sci 2007;16(7):1429-38.
Osawa M, Erickson HP. FtsZ from divergent foreign
bacteria can function for cell division in Escherichia
coli. J Bacteriol 2006;188(20):7132-40.
Chen Y, Erickson HP. Rapid in vitro assembly dynamics
and subunit turnover of FtsZ demonstrated by fluorescence
resonance energy transfer. J. Biol. Chem. 2005;280:22549-22554.
Anderson DE, Gueiros-Filho FJ, Erickson HP. Assembly
Dynamics of FtsZ Rings in Bacillus subtilis and Escherichia
coli and Effects of FtsZ-Regulating Proteins. J Bacteriol
2004;186(17):5775-81.
Erickson HP. Gene knockouts of c-src, TGF-beta1, and
tenascin suggest superfluous, non-functional expression
of proteins. Journal of Cell Biology 1993;120:1079-1081.
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Current
Projects and Lab Personnel
David Anderson (postdoc): FtsZ assembly
dynamics (single molecule TIRF).
Masaki Osawa (postdoc): Extragenic repressors
of FtsZ mutants.
Yaodong
Chen (postdoc): Fluorescence assays of FtsZ assembly
dynamics.
Christopher Lemmon (postdoc): Mechanical properties of the extracellular matrix; fibronectin mutations.
Tomoo Ohashi (postdoc): Fibronectin matrix assembly
and elasticity. |
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