"The E41K mutation inhibits troponin's ability to shift Tpm to the closed position at high Ca(2+) thus restraining the transition of the thin filaments from the "off" to the "on" state. The mutation also inhibits the ability of S1 to shift Tpm to the open position decreases the amount of the myosin heads bound strongly to actin at high Ca(2+) but increases the number of such heads at low Ca(2+)."xsd:string