Vertebrate Phototransduction

Question 1

Mammalian CNG channels modulated by Ca2+ in cones but not rods

Answer 1

Rebrik and Korenbrot, 2004

Question 2

CaM does not appear to be responsible for CNG regulation in cones (but is in rods)

Answer 2

Haynes and Stote (1997)

Question 3

R* may activate 20 transducin alpha molecules

Answer 3

Krispel et al, 2006

Question 4

Transducing channels have low affinity (1% open in darkness)

Answer 4

Yau and Baylor (1989)

Question 5

Intracellular Ca2 has strong effect on light-sensitive channel opening, but channels not simply dependent on Ca2+

Answer 5

Hodgkin et al, 1985

Question 6

0Na+/0Ca2+ solution → photoreceptor light adaptation mediated by cytoplasmic calcium concentration

Answer 6

Matthews et al, 1988

Question 7

G-protein deactivation rate-limiting for shutoff of phototransduction cascade

Answer 7

Sagoo and Lagnado, 1977

Question 8

Variation in rhodopsin kinase expression alters dim flash response shutoff and light adaptation

Answer 8

Sakurai et al, 2011

Question 9

Quenching of meta-II dominates time constant of recovery; changes in pH affect meta-I/meta-II equilibrium

Answer 9

Zang and Matthews, 2012

Question 10

Ca2+-CaM binds directly to CNG channel to reduce likelihood of opening

Answer 10

Li et al, 1994

Question 11

Membrane GC complexes shape photoresponses; GCAPs suppress cGMP synthesis in darkness

Answer 11

Wen et al, 2014