INVESTIGADORES
ADAMO Hugo Pedro
congresos y reuniones científicas
Título:
Involvement of the "A domain" in the autoinhibition of the plasma membrane Ca2+ pump
Autor/es:
MAZZITELLI LUCIANA ROMINA; ADAMO HUGO PEDRO
Reunión:
Congreso; VII Iberoamerican Congress of Biophysics; 2009
Resumen:
It has been proposed that the autoinhibition of the Ca2+ pump
of plasma membrane (PMCA) involves the blockage of the active site of the
enzyme by the C-terminal segment. Ca2+-calmodulin binds to the
C-terminal segment and stops inhibition.
Recent studies in other members of the P-type ATPase family indicate
that the A domain controls the access to the transport site which is buried in
the transmembrane region of the molecule. The amino acid segment Ile206-Val271
on the top of A domain of the PMCA has been directly implicated in the
interaction with the C-terminal segment. However, studies of other
autoinhibited pumps, suggest that autoinhibition can be controlled by a
structure at the bottom of domain A formed by the residues that connect this
domain with the transmembrane segments. We have investigated the functional
effect of domain A substitutions Ile227Ala, Asp223Ala, and
Glu99Gln, this latter residue located in the connecting stretch
between domain A and transmembrane segment M1. Substitutions Ile227Ala
and Asp223Ala led decreased the maximal activity to 45 % and 10 %,
respectively. In contrast the maximal activity of mutant Glu99Gln
was equal or higher than that of the wild type enzyme. In the absence of
calmodulin the activity of the Ile227Ala mutant was reduced to 66%
of the maximal activity suggesting that autoinhibition was taking place. While
mutants at Ile227 and Asp223 reduced the activity of the enzyme probably by
altering the structure of domain A, Glu99 together with residue Asp170
identified previously (Bredeston and Adamo, 2004) may be part of a negatively charged structure
required for autoinhibition of the PMCA.
(With Grants from UBA, CONICET and
ANPCyT Prestamo BID PICT 15-25965)