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Receptor Mech > Potassium structure > Flashcards

Potassium structure Flashcards

1
Q

Selectivity filter

A

TXGYGD MacKinnon 03/05 - P loop

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2
Q

What varies between Kv’s?

A

NTD and CTD typically short but can vary

Some can be heterotetrameric

Different alpha - each Kv gene encodes a Kva

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3
Q

Similar features of Kv’s?

A

Ampiphilic helix between S4 + S5 - links to S6T and next subunit

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4
Q

S6T does what

A

regulates open/close kv gates

PXP - typically valine for X

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5
Q

Non-specific blockers of Kv’s

A

4-AP + TEA Grissler 1994

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6
Q

A types

A

Shaker Kv1.4

All Shal Kv4

Shaw Kv3.3 + 3.4 - Birnbaum 2004

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7
Q

Structural differences of A type

A

Long NTD - ball and chain inactivation

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8
Q

Why is A-type inactivation N-type inactivation

A

Hoshi 1990

cytoplasmic trypsin - increase open duration and mean number of opening and burst

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9
Q

A-type effects on AP

A
  • activate relative -ve
    2. open in response to stimulus before cell reaches threshold
    3. recover from inactivation when hyperpolarised (by IDr)
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10
Q

A-type functional properties

A
  1. Delay between 1 AP and next (depends on stimulus size + type of A channel
  2. Regulate firing frequency, spike initiation + waveform -
  3. Regulate backward spread of AP and integration of EPSP Hoffman 1997
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11
Q

DR includes

A

Kv1 except 1.4, 2, 3.1, 7, 10.1

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12
Q

Structure of DR

A

Same as A without NTD inactivation particle

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13
Q

Current of DR

A

Outwardly rectifying with delay following dep. - prolonged and sustained current due to lack of N-type inactivation

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14
Q

DR functional properties

A

set neuronal RMP

IM - inhibitory influence on excitabiliy that counters repetitive or burst firing w/o affecting single AP’s

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15
Q

Inward rectifiers

A

Kir1-7

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16
Q

Structure of Kir6.1/6.1

A

SUR 4 subunits (SUR1,2A, 2B) 4 Kir6.1/6.2

17
Q

Kir function

A

frequency help set rmp

18
Q

Kir6.1/6.2 function

A

While ATP and ADP bind to IC side causes channel closure - when Mg2+ bound - molecules interact with nucleotide binding domains of SUR to increase channel activity

19
Q

Where are NBD of SUR

A

Between TMD1 and end of TMD2

20
Q

Where does ATP and ADP bind on SUR/Kir

A

Between TMD1 +2 - end of TMD2 (ADP) and between M1 and M2

21
Q

Ca2+ dep conductances

A

BK - 100-300pS

SK 1-25 pS

IK 25-100pS

22
Q

SK families

A

1-3

23
Q

Calcium bowl

A

RCK 2 - string of negative charges - cradle

24
Q

BK structure

A

alpha + 4 beta subunits - 1+4 excitatory

25
Q

BK current

A

Activated by voltage- become more active as membrane depolarizes or as IC ca2+ levels rise ( outwards rectification)

26
Q

BK functional properties

A
  1. help repolaarize membrane + turn of Ca2+ channels - end ecocytosis
  2. -ve feedback in response to raised IC ca2+
  3. smooth muscle relaxation - Brenner 2000 - KO -intention tremor, slow wim speed - decrease stride length
27
Q

SK structure

A

Calmodulin in CTD confers ability to respond to Ca2+

28
Q

SK current

A

can only be opened by increase IC ca2+ S4 less positive charges

29
Q

Functional properties of SK

A
  1. Hyperpolarization of cells after AP
  2. Ca2+ influx through synaptic NMDAR - activate SK -> hyperoplarize -> restore Mg2+ blcok
  3. Participate in vasoregulation , auditory tuning + circadian rhythm
30
Q

K2P members

A

15 - 5 categories - TREK, TWIK, TASK, THIK and TALK

31
Q

K2P structure

A
  • 2 kir sown together
    2. pore cap - helical regions of receptor protein
    3. 2 subunits form channel
32
Q

Significance of pore cap

A
  1. Prevents block by peptide toxins and small molecules - insensitive to TEA - that typically bind to ecternal mouth and pulg pore
  2. prevent efflux in vertical domain
  3. Facilitates partial rehydraation of K+ as they exit - outward rectification
33
Q

Functional purpose of K2P

A

RMP

34
Q

Functional purpose of IKCA

A

RBS channel activation - reduction inc ell volume - K+ effluc with Cl- and H20

Receptor Mech (25 decks)

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