DIDS binding 30-kDa protein regulates the calcium release channel in the sarcoplasmic reticulum

The gating properties of the Ca2+ release channel in the heavy fraction of the sarcoplasmic reticulum (HSR) was monitored by measuring the choline permeation through the channel using a light scattering method. The choline permeation was increased by the treatment of the HSR vesicles with 4,4'-diisothiocyano-stilbene-2,2'-disulfonic acid (DIDS), and this effect was only observed at low extravesicular Ca2+ concentrations. This result indicates that DIDS locked the Ca2+ channel at the open state. An SDS-PAGE of the junctional face membrane (JFM) that was treated with 3H2-DIDS showed that 3H2-DIDS binding protein is not the Ca2+ release channel but the 30 kDa protein. Furthermore, it was found that this 30 kDa protein is also one of the calsequestrin interacting proteins. These results suggest that this 30 kDa protein regulates the Ca2+ release channel.