Exam IV

Question 1

Notable dimeric families

Answer 1

CLC chloride channels
TMEM16 anion channels

Both of these families have two separate ion conduction pathways, one in each subunit of the dimer

Question 2

How do most channels form

Answer 2

Most ion channels assemble as various multimers, rarely dimers – in each case, the multimer creates a single, central pore through which ions can pass

With dimers (which is rare), subunits form 2 separate ion conduction pathways

Question 3

2 most closely related homologs

Answer 3

nhTMEM16

mmTMEM16A

Question 4

Most salient effect of MTSET in cochlear IHCs

Answer 4

Reduction in mean current amp

half M412C
3/4 D528C

Question 5

Sites reactive to MTSET

Answer 5

G411C, M412C, D528C, T532C, and D569C

Concl: must be accessible to aqueous solutions
must be within the permeation path for sensory transduction channels

Since MTSET is a charged, polar compound, it is not membrane permeable; thus, the reactive cysteines within transmembrane domains must be facing the channel’s aqueous pore and not the interface with the lipid membrane or other transmembrane domains

Question 6

MTS reagants

Answer 6

MTSET - small, pos charge
METSEA - smaller, pos charge
METSES - neg