Harold P. Erickson, Ph.D. (Johns Hopkins University)
James B. Duke Professor,
Department of Cell Biology
Programs: Cell and Molecular Biology, Structural Biology and Biophysics
412 Nanaline Duke Bldg., Box 3709
Duke University Medical Center
Durham, NC 27710
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. Recent discoveries include:
• The Z ring is very dynamic, exchanging subunits with a half time of 8 s.
• Reconstitution of Z rings in vitro. We provided FtsZ with a membrane tether, and found that when incorporated inside liposomes, membrane-targeted FtsZ can assemble Z rings without any other proteins.
• These reconstituted Z rings can also generate a constriction force on the membranes, again without any other proteins (no motor molecules).
• The constriction force is generated by a curved conformation of the protofilaments generating a bending force on the membrane.
• Negative stain EM of artificial Z rings shows ribbons of protofilaments, contradicting the prevailing view from cryoEM tomography of scattered protofilaments
Our long term goals are two-fold. First, to understand the mechanism of bacterial cell division. Second, to learn basic principles of assembly and mechanics that will apply to both FtsZ and 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.
Erickson HP (2013) Irisin and FNDC5 in retrospect: An exercise hormone or a transmembrane receptor? Adipocyte 2(4):289-93
Osawa M, Erickson HP (2013) Liposome division by a simple bacterial division machinery. Proc Natl Acad Sci USA 110(27):11000-4
Garder KA, Moore DA, Erickson HP (2013) The C-termial linker of Escherichia coli FtsZ functions as an intrinsically disordered peptide. Mol Microbiol 89(2):264-75
Milam SL, Osawa M, Erickson HP (2012) Negative-stain electron microscopy of inside-out FtsZ rings reconstituted on artificial membrane tubules show ribbons of protofilaments. Biophys J. 103(1):59-68
Chen Y, Milam SL, Erickson HP (2012) SulA inhibits assembly of FtsZ by a simple sequestration mechanism. Biochemistry 51(14):3100-9
Erickson HP (2011) Race disparity in grants: check the citations. Science 334(6058):899
Ohashi T, Erickson HP (2011) Fibronectin aggregation and assembly: the unfolding of the second fibronectin type III domain. J Biol Chem 286(45):39188-99
Lemmon CA, Ohashi T, Erickson HP (2011) Probing the folded state of fibronectin type III domains in stretched fibrils by measuring buried cysteine accessibility. J Biol Chem. 286(30):26375-82