Which one of the following statements concerning the ryanodine receptor calcium

Question

Which one of the following statements concerning the ryanodine receptor calcium release channel in malignant hyperthermia susceptible muscle is incorrect?

            a.         RYR1 mutations that cause muscle disorders are clustered into “hotspots” in the primary amino acid sequence.

                         b.         In malignant hyperthermia susceptible muscle more calcium is released from the SR in the presence of halothane than in normal muscle.

            c.         RYR1 mutations that cause central core disease have a more deleterious effect on channel function than RYR1 mutations that only cause malignant           hyperthermia susceptibility.

                        d.         Isolated RYR1 calcium channels from malignant hyperthermia susceptible individuals have an increased channel open probability at any activating  Ca2+   concentration.

                          e.         Isolated RYR1 calcium channels from malignant hyperthermia susceptible individuals are     always open, even at very low stimulatory Ca2+.

Explanation / Answer

e. Isolated RYR1 calcium channels from malignant hyperthermia susceptible individuals are always open.

Calcium channel opening probability in RYR1 varies with heterogenous and homogenous RYR1 susceptibility. Open state is stable in homogenous and closed state is favored by heterogenous RYR1.

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