28. (6) Certai migraines, such as a channel shown below channels containing wt o

Question

28. (6) Certai migraines, such as a channel shown below channels containing wt or R1920 mutant in HEK293 cells transiently expressin are shown below. Step depolarizations were delivered from a holding potential of -90 m shown below are elicited by step depolarizations between-50 and 0 mV (left panels) in 10 mV increments (ignore right panels). in mutations in ion channels have been found in individuals with familial hemiplegic . Whole-cell patch-clam p recordings of human recombinant g the channel subunits V. Currents wt 00 pA R1920 800 pA a. Does this channel inactivate? Yes or No b. Is the channel opening voltage-dependent? Yes or No c. What direction is the current flow shown in this experiment (circle answer)? IN or OUT d. What ion (or ions) is (are) likely responsible for this current? e. How could you experimentally determine which ion flows through the channel? f. Describe how the channel properties differ in the R1920 mutant from the wild type.

Explanation / Answer

A. No , becuase of hinderence of Ca ions channel mainly.

B.Yes , becuase in this type of mutation ions channel open at more negative potential.

C. IN , because direction of current flow is same as in case of non -mutant ion channels

D. Mainly Na+ and K+ ions becuase it cause potential gradient across the neurons.

E. As Pre pulse facilitation is a property of Voltage dependent ion channels which is reduced by R192Q , Facilitation kinetatics slow activity suggests that mutantion of G -protien P/Q type Ca+ ion channel.

F. In R192Q mutation , there is high probability of channel opening than wild type.

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