Biophysical Society Thematic Meeting - October 25-30, 2015

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

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