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SUMMARY:Metal cofactor assembly in chloroplasts - Dr Marinus Pilon\, Color
 ado State University
DTSTART:20061012T150000Z
DTEND:20061012T160000Z
UID:TALK5283@talks.cam.ac.uk
CONTACT:3901
DESCRIPTION:Metal cofactor assembly in chloroplasts\n\nDr Marinus Pilon\, 
 Colorado State University\n\nGenomic analyses have indicated that about a 
 third of all proteins require a metal cofactor for activity. Cells must re
 gulate and prioritize the delivery of metal ion cofactors by membrane tran
 sport processes to targets in various organelles. The growth environment o
 ften limits the availability of metal cofactors. Under limitation cells sh
 ould therefore prioritize delivery to specific targets and coordinate deli
 very with apo-protein expression as well as varying metabolic demand. Targ
 ets for Cu delivery in plant chloroplasts are plastocyanin in the thylakoi
 ds and Cu/Zn-superoxide dismutase (Cu/ZnSOD) in the stroma. PAA1 and PAA2 
 encode Cu-transporting P-type ATPases. Characterization of paa1 and paa2 m
 utants showed that the two transporters have distinct functions\; whereas 
 both transporters are required for Cu delivery to plastocyanin and efficie
 nt electron transport\, Cu delivery to the stroma is only inhibited in paa
 1 but not in paa2 mutants. Localization experiments show that both transpo
 rters function in chloroplasts and that the PAA1 protein is in the chlorop
 last periphery. A paa1 paa2 double mutant was seedling lethal and could no
 t be rescued by Cu feeding. A third component of the Cu delivery system in
  chloroplasts is CCS\, a Cu-chaperone that delivers Cu to Cu/ZnSOD. Next t
 o Cu/ZnSOD\, plants have a FeSOD in the chloroplast. Interestingly\, Cu av
 ailability regulates the activity of the SOD isoforms. At low Cu levels\, 
 the FeSOD is active and Cu/ZnSOD and CCS expression is shut off\, so that 
 Cu is preferentially targeted to plastocyanin\, which is essential in plan
 ts. At higher Cu levels\, FeSOD expression is shut off saving Fe for other
  uses\, and Cu/Zn SOD becomes a sink for Cu in the stroma. We found a sign
 aling pathway\, which senses the Cu that is available to the chloroplast a
 nd which mediates the down-regulation of non-essential nuclear-encoded Cu-
 proteins under Cu limitation.\n\nMore details as well as links to his exce
 llent publications can be found at http://rydberg.biology.colostate.edu/ep
 smitslab/
LOCATION:Department of Plant Sciences\, Large Lecture Theatre
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