Page 232 - Color Atlas of Biochemistry

Biological membranes 223

A. Voltage-gated Na + channel

I II III IV

2 3
1 4
12 3 4 5 6 6 5

N C
a Membrane
Narrow pore polarized,
helix 4
Na in position 1
Pore α-Subunit
4
3
2
Voltage- Outside 5
sensitive 1 6
helix
(helix 4)

Inside b Membrane
depolarized,
Wide pore helix 4
in position 2
1. Structure 2. Mechanism Na

B. Nicotinic acetylcholine receptor

N α C δ β α γ δ β
α L α H

Acetyl-
choline
Subunits
Na
Helix 2

1. Structure 2. Pore 3. Mechanism
+
C. K channel in Streptomyces lividans
A B C D
Outside

Plasma-
membrane
Subunits
Outside

Inside
Plasma
membrane

Inside
K
Homotetramer From above

Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme
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