Engineering Approaches to Biomolecular Motors

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Engineering Approaches to Biomolecular Motors: From in vitro to in vivo Friday Speaker Abstracts
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Transportation of Artificial Cargos by the Par and Min Systems
James A. Taylor1, Anthony G. Vecchiarelli1, Keir C. Neuman2, Kiyoshi Mizuuchi 1.
1NIH, Bethesda, MD, USA, 2NIH, Bethesda, MD, USA.
Spatial organization and active transportation of cellular contents are essential for cellular
division. This is true even in bacteria, which were once thought too simple to require much
internal organization. The ubiquitous deviant Walker ATPase family of proteins has been shown
to be involved in systems important for spatial coordination in bacteria, the two most highly
studied examples of which are the DNA partitioning Par system and the divisome positioning
Min system. Both these systems contain the eponymous deviant Walker A ATPase (ParA or
MinD), a protein which stimulates the ATPase’s hydrolysis activity (ParB or MinE) and a cargo
to be transported or localized (the “centromere” DNA site cluster bound by ParB or the divisome
inhibitor MinC bound to MinD). Despite the similarities of their components these systems
appear to behave quite differently in vivo: the Par system segregates large clusters of ParB bound
DNA cargo into sister cells during division by displacing ParA non-specifically bound to the
nucleoid whereas the Min proteins bind the inner membrane and are seen to oscillate from one
cell pole to the other. These differences may arise due to the nature of the binding surface (DNA
vs lipid) or the nature of the cargo (a large cargo bound by a large number of stimulator protein
molecules in Par vs small protein molecules individually bound to membrane-bound MinD
dimers). Here we use TIRF microscopy demonstrating that the Min system is capable of
transporting a magnetic bead (a large cargo) along a supported lipid bilayer in a manner
strikingly similar to our previous reconstitution of the Par system. This demonstrates that despite
their clear differences in their system dynamics under conditions for their natural functions, Par
and Min systems operate based on common underlying mechanistic principles.
Mechanics and Design of Active Matter Constructed from Actomyosin
Margaret Gardel
University of Chicago, Chigago, IL, USA
No Abstract