Ca2+ transport and heat production in vesicles derived from the sarcoplasmic reticulum terminal cisternae: regulation by K+.
In this work, we compared the effect of K+ on vesicles derived from the longitudinal (LSR) and terminal cisternae (HSR) of rabbit white muscle. In HSR, K+ was found to inhibit both the Ca2+ accumulation and the heat released during ATP hydrolysis by the Ca2+-ATPase (SERCA1). This was not observed in LSR. Valinomycin abolished the HSR Ca2+-uptake inhibition promoted by physiological K+ concentrations, but it did not modify the thermogenic activity of the Ca2+ pump. The results with HSR are difficult to interpret, assuming that a single K+ is binding to either the ryanodine channel or to the Ca2+-ATPase. It is suggested that an increase of K+ in the assay medium alters the interactions among the various proteins found in HSR, thus modifying the properties of both the ryanodine channel and SERCA1.
Nigro
Mariana
M
Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Cidade Universitária, RJ, 21941-902, Brazil.
Arruda
Ana Paula
AP
de Meis
Leopoldo
L
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D006358:Hot Temperature; D006868:Hydrolysis; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011817:Rabbits; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism
D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D011188:Potassium; D002118:Calcium