Ability of nucleoside triphosphates to provide for Ca 2+ transport by sarcoplasmic reticulum fragments

The Ca2+ transport by sarcoplasmic reticulum fragments was studied. ATP, CTP, ITP, GTP and UTP provided the same Ca-pump efficiency. When the NTP was exhausted, Ca2+ actively accumulated from the sarcoplasmic reticulum vesicles outflow, and with the higher rate of ATP was a substrate. The Ca-ATPase conformational transitions induced by ATP are discussed for their role in the provision of energy.