The Conversion of Osmotic into Chemical Energy Coupled with Calcium Translocation across the Sarcoplasmic Membrane
This extract was created in the absence of an abstract.
Excerpt
In the last year it was demonstrated that the sarcoplasmic calcium pump can run backwards (Barlogie et al., 1971; Makinose, 1971; Makinose and Hasselbach, 1971). Typical experimental conditions for the backward reaction are shown in Fig. 1. The vesicles were loaded with calcium in a solution containing 2 mm acetyl phosphate, 7 mm MgCl2, 20 mm inorganic phosphate, and 0.2 mm calcium. An addition of 1 mm EGTA after the completion of the calcium uptake induces only a very slow calcium release. When 2 mm ADP is added to this system, one observes a rapid calcium efflux and a simultaneous synthesis of ATP from ADP and inorganic phosphate present in the solution. For every two calcium ions released from the vesicles, one molecule of ATP is synthesized. This result and further analysis show that, for the rapid calcium efflux coupled with ATP synthesis, the following conditions must be fulfilled: ADP...
