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SUMMARY:Structure and mechanism of the tripartite CusCBA heavy-metal efflu
 x complex - Professor Edward Yu\, Iowa State University
DTSTART:20120709T140000Z
DTEND:20120709T150000Z
UID:TALK38938@talks.cam.ac.uk
CONTACT:14931
DESCRIPTION:Gram-negative bacteria frequently expel toxic chemicals throug
 h tripartite\nefflux pumps that span both the inner and outer membranes.  
 The three\nparts are the inner membrane\, substrate-binding transporter (o
 r pump)\; a\nperiplasmic membrane fusion protein (or adaptor)\; and an out
 er\nmembrane-anchored channel.  The fusion protein connects the transporte
 r to\nthe channel within the periplasmic space.  One such efflux system Cu
 sCBA\nis responsible for extruding biocidal Cu(I) and Ag(I) ions.  We prev
 iously\ndescribed the crystal structures of both the inner membrane transp
 orter\nCusA and the membrane fusion protein CusB of E. coli.  We also dete
 rmined\nthe co-crystal structure of the CusBA adaptor-transporter efflux c
 omplex\,\nshowing that the transporter CusA\, which is present as a trimer
 \, interacts\nwith six CusB protomers and that the periplasmic domain of C
 usA is\ninvolved in these interactions. Here\, we summarize the structural
 \ninformation of these efflux proteins\, and present the accumulated evide
 nce\nthat this efflux system utilizes methionine residues to bind and expo
 rt\nCu(I) and Ag(I).  Genetic and structural analyses suggest that the Cus
 A\npump is capable of picking up the metal ions from both the periplasm an
 d\ncytoplasm.  We propose a stepwise shuttle mechanism for this pump to\ne
 xport metal ions from the cell.\n
LOCATION:Department of Biochemistry\, Hopkins Building\, Seminar Room 1
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