ibclogo XVI International Botanical Congess


Abstract Number: 2951
Session = 7.17.7


STRUCTURE AND FUNCTION OF CALCIUM PUMPS


Jeff Harper, Scripps Research Inst., La Jolla CA 92037


Two families of Ca2+-pumps have been identified in Arabidopsis. Representatives include: ECA1, type-IIA (ER-type) and ACA2, type-IIB (PM-type). Compared to animal homologs, ACA2-like pumps are novel in two respects: 1) They have non-plasma membrane locations (eg. ACA2 is in ER instead of PM, Plant Physiol 119: 1165, 1999). 2) They share a unique organization in which a calmodulin-regulated autoinhibitor is located at the N- instead of C-terminus. Both ECA1p and ACA2p can function in the yeast host K616 to complement a deletion of the yeast Ca2+-pumps. However, complementation by ACA2 occurs only when the pump is mutated to be calmodulin-independent (ie. de-regulated). This yeast system provides the first genetic selection to identify mutations that disrupt the regulatory mechanism of a calmodulin-dependent Ca2+-pump. Deregulated Ca2+-pumps may be useful in transgenic plants to disrupt Ca2+ signals.


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