Calcium channels Flashcards
Depolarisation
After depolarisation there is a rapid increase of calcium ions but it is followed by a decline which is inactivation
different voltages CaV channels
lva-Low voltage activated
Hva-High voltage activated
subunits of calcium channel
Alpha 2 is a extracellular protein and delta subunit is a transmembrane protein form together
Pore of calcium channel
Pore is formed by a pair of charged glutamate residue and is important for the selectivity of calcium ions\4 hydrophobic residue at the inner gate and they are water insoluble and can block calcium ions
subunits movement when
When depolarisation occurs voltage sensing domain move outwards of the membrane pulling the s4 s5 domain
What modulates caV
Calcium dependent facilitation and inactivation of Cav channels
Calcium dependent facilitation promote activation of calcium channels but CDI can cause inactivation
What modulates calcium inactivation
Calcium inactivation is modulated by calmodulin
Calmodulin is a sensor and have to lobes in which calcium can bind to, C lobe has a higher affinity than N lobe
Calcium functions
Calcium is also an important signalling messenger which causes CDI but also gene transcription in the nucleus
LTP from caV
Activation of nerve cells in the brain can cause long term potentiation mediated by calcium and enhance learning ability
Excitation transcription coupling
Cav 1.2 channels when activated caclium flows into cells and can bind to calmodulin which actives CaN which de-phosphorylates a transcription factor NFAT
Once de-phosphorylated it goes to the nucleus to promote gene transcription change
Excitation transcription coupling pt.2
Cav 1.3 when activated it increases calcium concentration in cytosol and combine to calmodulin which can bind to CamKII beta it can then bind to the C terminal. activate CaMMK to catalyse reaction of CaMK4 which can activate a transcription factor(CREB)
