[CSBi-events] CSBi Speaker Series-4/20/06 (Dr. C. Bustamante)

[CSBi events]

Dear CSBi Community,

This message simply serves to inform you of our 
upcoming CSBi Speaker Series event on Thursday, 
April 20th. Please note, this event will be held 
in
Building 4, room 270. We sincerely hope that you 
will join us if your schedule permits.  Thank you.

Dr. Carlos Bustamante
Professor of Molecular and Cell Biology, Physics and Chemistry
and
Howard Hughes Medical Institute Investigator
University of California, Berkeley

"Direct Observation of Substeps Reveals the RNA Unwinding Mechanism of
HCV NS3 Helicase"

Thursday, April 20, 2006
Maclaurin Building (4-270)
3:00 - 4:00 p.m.
Light refreshments served at 2:45 p.m.

Abstract
	Helicases are a ubiquitous class of 
enzymes involved in nearly all aspects of DNA and 
RNA metabolism. Despite recent progress in 
understanding their mechanism of action, limited 
resolution has left inaccessible the detailed 
mechanisms by which these enzymes couple the 
rearrangement of nucleic acid structures to the 
binding and hydrolysis of ATP. Observing 
individual mechanistic cycles of these motor 
proteins is central to understanding their 
cellular functions. Here we follow in real time, 
at a resolution of two base pairs and 20 ms, the 
RNA translocation and unwinding cycles of a 
hepatitis C virus helicase (NS3) monomer. NS3 is 
a representative superfamily-2 helicase essential 
for viral replication and therefore a potentially 
important drug target. We show that the cyclic 
movement of NS3 is coordinated by ATP in discrete 
steps of 11±3 base pairs, and that actual 
unwinding occurs in rapid smaller substeps of 
3.6±1.3 base pairs, also triggered by ATP 
binding, indicating that NS3 might move like an 
inchworm. This ATP-coupling mechanism is likely 
to be applicable to other non-hexameric helicases 
involved in many essential cellular functions. 
The assay developed here should be useful in 
investigating a broad range of nucleic acid 
translocation motors.

Host:		Dr. Robert T. Sauer		Biology Department

                               Contact:	Brenda E. Pepe
	617.253.6077

Sponsored by CSBi
http://csbi.mit.edu/
Annual CSBi Seminar Series in Computational and Systems Biology
The entire MIT Community is welcome to attend!
-- 
Brenda E. Pepe
Administrative Assistant to Professor Christopher B. Burge
Massachusetts Institute of Technology
Department of Biology, 68-223
31 Ames Street
Cambridge, MA  02139
Tel:  617-452-3885
Fax: 617-452-2936