Auto-inhibition of Arabidopsis thaliana plasma membrane Ca2+-ATPase involves an interaction of the N-terminus with the small cytoplasmic loop.
Type IIB Ca2+-ATPases have a terminal auto-inhibitory, domain the action of which is suppressed by calmodulin (CaM) binding. Here, we show that a peptide (6His-1M-I116) corresponding to the first 116 aminoacids (aa) of At-ACA8, the first cloned isoform of Arabidopsis thaliana plasma membrane Ca2+-ATPase, inhibits the activity of the enzyme deprived of the N-terminus by controlled trypsin treatment 10-fold more efficiently than a peptide (41I-T63) corresponding only to the CaM-binding site. A peptide (268E-W348) corresponding to 81 aa of the small cytoplasmic loop of At-ACA8 binds peptide 6His-1M-I116 immobilized on Ni-NTA agarose. Peptide 268E-W348 stimulates Ca2+-ATPase activity. Its effect is not additive with that of CaM and is suppressed by tryptic cleavage of the N-terminus. These results provide the first functional identification of a site of intramolecular interaction with the terminal auto-inhibitory domain of type IIB Ca2+-ATPases.
Luoni
Laura
L
Dipartimento di Biologia L. Gorini, Università di Milano, CNR Istituto di Biofisica--Sezione di Milano, via G. Celoria 26, 20133 Milano, Italy. laura.luoni@unimi.it
Meneghelli
Silvia
S
Bonza
Maria Cristina
MC
DeMichelis
Maria Ida
MI
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology*; D001483:Base Sequence; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D002462:Cell Membrane / Q000201:enzymology; D003593:Cytoplasm / Q000378:metabolism*; D017931:DNA Primers; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D000252:Calcium-Transporting ATPases