Transcript Phototransduction • Retina and photoreceptor Rhodopsin

Phototransduction
•Retina and photoreceptor
•Rhodopsin
•Excitation - recovery/adaptation
•Cyclic nucleotide gated channels
Eric Niederhoffer
SIU-SOM
Retina and Photoreceptor
http://www.fz-juelich.de/inb/inb-1/Photoreception/
http://www.mardre.com/homepage/mic/tem/samples/bio/ros/rosdiag.html
Rhodopsin
O
bathorhodopsin
11
H
12
lumirhodopsin
Rhodopsin*
metarhodopsin I
Metarhodopsin II (t1/2 ~ 60 s)
h
Opsin + trans-retinal
11
12
retinol
O
Rhodopsin
H
cis-retinal
RPE
Excitation - Recovery/Adaptation
hv
GTP
GDP
Tbg Ta
Rh GDP
c-tR
Rh
tR
cR
RK
Rc
Low
[Ca2+]
Ta
GTP
I
PDE
CaM
CNGC
PDE
RPE65
Excitation
tR
Recovery/Adaptation
Rh
tR
GMP
Ta I
GTP
cGMP
cGMP
K+
Ca2+
GC
cGMP
Arr
Low
[Ca2+]
GCAP-1
GTP
cGMP
cGMP
Na+
Ca2+
Na+
Review Questions



Which ions and ion channels are used
for phototransduction?
Which signal transduction pathway is
used for phototransduction (enzymes,
second messenger, receptor)?
How does phototransduction compare
with gustation and olfaction?