Phosphorylation of the Ca2+ pump intermediate in intact red cells,isolated membranes and inside-out vesicles |
| |
Authors: | Ilma Szász Maria Hasitz Balázs Sarkadi George Gárdos |
| |
Institution: | (1) Department of Cell Metabolism, National Institute of Haematology and Blood Transfusion, 1113 Budapest, Hungary |
| |
Abstract: | Summary Ca2+-entry into intact red cells containing 32P]-ATP increases the phosphorylation of the 150 000 dalton polypeptide of the membrane. This phosphorylation occurs even in Mg2+-depleted red cells. Extracellular lanthanum applied during ATP-depletion further increases the Ca 2+ -induced phosphorylation.In fragmented membranes or resealed insideout vesicles (IOVs) membrane bound Mg2+ is sufficient to catalyze the phosphorylation of spectrin 2 and Band 3 polypeptides with low concentrations (< 1 M) of 32P]-ATP. In Ca-EDTA buffers one single polypeptide is phosphorylated which is located in the 150 000 molecular weight region. KmCa for phosphorylation is much lower (0.2 m) than for active Ca2+ transport (40 M) in IOVs. Lanthanum induced phosphorylation (up to 250 m Lafree) is significantly greater than Ca2+-induced phosphorylation. Hg2+ inhibits both Ca2+ and La3+ induced phosphorylation. Ca2+-induced labelling can be rapidly chased by unlabelled ATP +Mg2+, but not with EGTA+Mg2+. Dephosphorylation in Ca 2+ phosphorylated membranes and IOVs is significantly inhibited by La 3+. It can be concluded that the mechanism of La and H g2+ inhibition of the Ca 2+ pump is different in intact cells and isolated membranes or IOVs.Abbreviations EDTA
ethylenediamine tetraacetate
- EGTA
ethyleneglycol-bis(2-aminoethylether)-N-N -tetraacetate
- IOV
inside-out vesicle
- SDS
sodium dodecylsulfate
- TCA
trichloroacetic acid |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |