A CALMODULIN-STIMULATED CA2-ATPASE FROM PLANT VACUOLAR MEMBRANES WITHA PUTATIVE REGULATORY DOMAIN AT ITS N-TERMINUS()

A cDNA, BCA1, encoding a calmodulin-stimulated Ca2+-ATPase in the vacu olar membrane of cauliflower (Brassica oleracea) was isolated based on the sequence of tryptic peptides derived from the purified protein. T he BCA1 cDNA shares sequence identity with animal plasma membrane Ca2-ATPases and Arabidopsis thaliana ACA1, that encodes a putative Ca2+ p ump in the chloroplast envelope. In contrast to the plasma membrane Ca 2+-ATPases of animal cells, which have a calmodulin-binding domain sit uated in the carboxy-terminal end of the molecule, the calmodulin-bind ing domain of BCA1 is situated at the amino terminus of the enzyme.