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  current news   Press   selected story    
     
  30th May 2012  
  A novel actin-like filament structure from Clostridium tetani
 
 




Authors
David Popp1#, Akihiro Narita2#, Lin Jie Lee1, Umesh Ghoshdastider3, Bo Xue1, Ramanujam Srinivasan4, Mohan K. Balasubramanian4,5,6, Toshitsugu Tanaka2 and Robert C. Robinson1,7,8

1 -
Institute of Molecular and Cell Biology, Proteos, 61 Biopolis Drive, Singapore, 138673.
2 -
Nagoya University Graduate School of Science, Structural Biology Research Center and Division of Biological Sciences, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan.
3 -
Institute for Biophysical Chemistry, Goethe University, Senckenberganlage 31, 60325 Frankfurt, Germany.
4 -
Mechanobiology Institute, National University of Singapore, T-Lab, #05-01 5A Engineering Drive 1, Singapore, 117411.
5 -
Temasek Life Sciences Laboratory, The National University of Singapore, 1 Research Link, Singapore, 117604.
6 -
Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore, 117543.
7 -
Department of Biochemistry, National University of Singapore, 8 Medical Drive, Singapore 117597.
8 -
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551.

# these authors contributed equally to this work

Published in Journal of Biological Sciences on April 18, 2012

Abstract

Eukaryotic F-actin is constructed from two protofilaments that gently wind around each other to form a helical polymer. Several bacterial actin-like proteins (Alps) are also known to form F-actin-like helical arrangements from two protofilaments, yet with varied helical geometries. Here we report a unique filament architecture of Alp12 from Clostridium tetani that is constructed from four protofilaments. Through fitting of an Alp12 monomer homology model into the electron microscopy data, the filament was determined to be constructed from two anti-parallel strands, each comprised of two parallel protofilaments. These four protofilaments form an open helical cylinder separated by a wide cleft. The molecular interactions within single protofilaments are similar to F-actin, yet interactions between protofilaments differ to those in F-actin. The filament structure and assembly and disassembly kinetics suggest Alp12 to be a dynamically unstable force-generating motor involved in segregating the pE88 plasmid, which encodes the lethal tetanus toxin, and thus a potential target for drug design. Alp12 can be repeatedly cycled between states of polymerization and dissociation making it a novel candidate for incorporation into fuelpropelled nano-biopolymer machines.

Figure Legend: Fig. 1 Three views of the Alp12 Filament. (A) Focusing on a parallel strand (yellow and red) with the second parallel strand (blue and cyan) related by an antiparallel manner. (B) Focusing on the trench. (C) The filament viewed end-on.



Figure Legend: Fig. 2 Repeated polymerization-depolymerization cycles visualized by light scattering. Alp12 (8 µM) could be cycled repeatedly through polymerization and depolymerization. At each green arrow 100 µM NTP was added. At the purple arrows 1 mM NTP was added. Red = ATP. Blue = GTP.

For more information on Robert ROBINSON's laboratory, please click here.