IQUIFIB   02644
INSTITUTO DE QUIMICA Y FISICOQUIMICA BIOLOGICAS "PROF. ALEJANDRO C. PALADINI"
Unidad Ejecutora - UE
artículos
Título:
Hyperactivation of the human plasma membrane Ca2+ pump PMCA h4xb by mutation of Glu99 to Lys
Autor/es:
MAZZITELLI LUCIANA ROMINA; ADAMO HUGO PEDRO
Revista:
JOURNAL OF BIOLOGICAL CHEMISTRY
Editorial:
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Referencias:
Lugar: Bethesda, Maryland; Año: 2014 vol. 289 p. 10761 - 10768
ISSN:
0021-9258
Resumen:
The transport of calcium to the extracellular space carried outby plasma membrane Ca2 pumps (PMCAs) is essential formaintaining low Ca2 concentrations in the cytosol of eukaryoticcells. The activity ofPMCAsis controlled by autoinhibition.Autoinhibition is relieved by the binding of Ca2-calmodulin tothe calmodulin-binding autoinhibitory sequence, which in thehuman PMCA is located in the C-terminal segment and resultsin a PMCA of high maximal velocity of transport and high affinityfor Ca2. Autoinhibition involves the intramolecular interactionbetween the autoinhibitory domain and a not welldefined region of the molecule near the catalytic site. Here weshow that the fusion ofGFPto theCterminus of the h4xbPMCAcauses partial loss of autoinhibition by specifically increasingthe Vmax. Mutation of residue Glu99 to Lys in the cytosolic portionof the M1 transmembrane helix at the other end of themolecule brought the Vmax of the h4xbPMCAto near that of thecalmodulin-activated enzyme without increasing the apparentaffinity for Ca2. Altogether, the results suggest that the autoinhibitoryinteraction of the extreme C-terminal segment of theh4PMCAis disturbed by changes of negatively charged residuesof the N-terminal region. This would be consistent with arecently proposed model of an autoinhibited form of the plantACA8 pump, although some differences are noted.