INVESTIGADORES
FERREIRA GOMES Mariela Soledad
artículos
Título:
Plasma Membrane Calcium Pump (PMCA) Differential Exposure of Hydrophobic Domains after Calmodulin and Phosphatidic Acid Activation.
Autor/es:
MANGIALAVORI I,; ANA MARIA VILLAMIL GIRALDO; MARÍA F. PIGNATARO; MARIELA FERREIRA GOMES; IARIEL .J. CARIDE ; JUAN PABLO F. C. ROSSI
Revista:
JOURNAL OF BIOLOGICAL CHEMISTRY
Editorial:
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Referencias:
Año: 2011 vol. 286 p. 18397 - 18404
ISSN:
0021-9258
Resumen:
The exposure of the plasma membrane calcium pump (PMCA) to the
surrounding phospholipids was assessed by measuring the incorporation
of the photoactivatable phosphatidylcholine analog [(125)I]TID-PC/16 to
the protein. In the presence of Ca(2+) both calmodulin (CaM) and
phosphatidic acid (PA) greatly decreased the incorporation of
[(125)I]TID-PC/16 to PMCA. Proteolysis of PMCA with V8 protease results
in three main fragments: N, which includes transmembrane segments M1
and M2; M, which includes M3 and M4; and C, which includes M5 to M10.
CaM decreased the level of incorporation of [(125)I]TID-PC/16 to
fragments M and C, whereas phosphatidic acid decreased the
incorporation of [(125)I]TID-PC/16 to fragments N and M. This suggests
that the conformational changes induced by binding of CaM or PA extend
to the adjacent transmembrane domains. Interestingly, this result also
denotes differences between the active conformations produced by CaM
and PA. To verify this point, we measured resonance energy transfer
between PMCA labeled with eosin isothiocyanate at the ATP-binding site
and the phospholipid RhoPE included in PMCA micelles. CaM decreased the
efficiency of the energy transfer between these two probes, whereas PA
did not. This result indicates that activation by CaM increases the
distance between the ATP-binding site and the membrane, but PA does not
affect this distance. Our results disclose main differences between
PMCA conformations induced by CaM or PA and show that those differences
involve transmembrane regions.