Troponin I converts the skeletal muscle ryanodine receptor into a rectifying calcium release channel.

The goal of our present studies has been to find novel ryanodine receptor (RyR1) interacting polypeptides that modulate the channel activity from the luminal side of RyR1. Using K(+) as charge carrier for recording of single channel events here we demonstrate a very unexpected observation that troponin I substantially alters RyR's gating behavior, and that RyR1 in association with troponin I becomes a rectifying Ca(2+) release channel. Troponin I rapidly locks the RyR1 in a non-conducting state only at a negative holding potential, and only when applied to the luminal side; switching to a positive holding potential results in the channel returning to its original activity, immediately.