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Evidence for direct involvement of the sarcoplasmic reticulum Ca 2+ ‐ATPase in a passive monovalent cation (K + /Na + ) exchange
Author(s) -
de Jesus Florence,
Cuillel Martine,
Dupont Yves
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(95)01267-1
Subject(s) - endoplasmic reticulum , chemistry , ion exchange , atpase , ion , enzyme , biochemistry , organic chemistry
A specific inhibitor of SERCA‐pumps, thapsigargin (TG) was used to demonstrate the direct involvement of the SR Ca 2+ ‐ATPase in passive K + /Na + exchange. The K + ‐potential variations across vesicle membranes were measured in the absence of ATP with a fluorescent probe: 3,3′‐dipropylthiodicarbocyanine iodide. Addition of EGTA dissipates the K + ‐potential whereas the presence of TG abolishes this effect. Our data prove that the Ca 2+ ‐ATPase translocates monovalent cations at a rate similar to the E 2 →E 1 conformational change.