Tetrodotoxin binds to and blocks the activity of a type of these proteins.
The selectivity filter for one type of these proteins is formed from alpha helices and P segments. Fruit flies with the shaker mutation have a defect in a type of these proteins, which can be studied using micropipettes in order to obtain a patch clamp recording. Tetrodotoxin binds to and blocks the activity of a type of these proteins. Action potentials are generated by the opening and closing of their voltage-gated type, while their ligand-gated type can respond to neurotransmitters.  For 10 points, name these proteins that allow charged atoms to move across a membrane. 
The selectivity filter for one type of these proteins is formed from alpha helices and P segments.
ion channels [accept specific types; prompt on "membrane proteins"] 