Every step we take begins with a burst of calcium inside our muscle cells, causing them to contract. To prepare for action, the cells keep calcium locked in an internal compartment, the sarcoplasmic reticulum. Studding its membrane are thousands of RyR1 channels—the largest known ion channels—th at contain pores that release the calcium. For a muscle to contract properly, RyR1 channels must open synchronously via a mechanism known as "coupled gating." How they accomplish this has been unclear since it was described almost 30 years ago. ...read more read less