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Polymers and Self Assembly: From Biology to Nanomaterials
Monday Speaker Abstracts
Building a Flagellum on the Bacterial Cell Surface.
Gillian M. Fraser
1
, Paul M. Bergen
1
, Lewis D. Evans
1,3
, Simon Poulter
1
, Eugene M. Terentjev
2
,
Colin Hughes
1
, Daniel Nietlispach
3
.
1
University of Cambridge, Cambridge, United Kingdom,
2
University of Cambridge, Cambridge,
United Kingdom,
3
University of Cambridge, Cambridge, United Kingdom.
Bacteria build helical propellers, called flagella, on their surface. Biologists and physicists have
long found flagella fascinating as they illustrate beautifully how complex structures self-
assemble to operate as nanomachines on the cell surface. During flagellum assembly, thousands
of subunits destined for the growing structure are made inside the cell, then unfolded and
exported across the cell membrane. Like other biological functions, this initial phase of export
consumes energy produced by the cell. But then the subunits pass into a channel at the centre of
the growing flagellum on the outside of the cell, and must transit a substantial distance to the
flagellum tip where they crystallise into the structure. In this way the flagellum grows at a
constant rate to several times the length of the cell.
The mystery has been how are flagellar subunits passed down the long channel far outside the
cell where there is no discernable energy source to propel them?
I will describe a simple and elegant mechanism that allows constant rate growth of the flagellum
outside the cell by harnessing the entropic force generated by the unfolded subunits themselves
as they link in a chain that is pulled to the flagellum tip. I will go on to present new NMR data
that reveal structural changes in the membrane export machinery as flagellar subunits bind prior
to capture into the export chain.
Reference
Evans LDB, Poulter S, Terentjev EM, Hughes C and Fraser GM (2013) A chain mechanism for
flagellum growth. Nature 504: 287-290
Self-Assembly of Actin in Cell Motility: From Molecules to Movement
Marie-France Carlier
Emory University, France
No abstract