active transportn.ethz.ch/~nielssi/download/4. semester/biological... · 2013. 3. 29. · active...
TRANSCRIPT
ACTIVE TRANSPORT
(from Berg, Tymoczko & Stryer, Biochemistry, 5th Ed.)
Calcium-ATPase(Toyoshima et al., Nature 2000, 405, 647-655)
Ca2+-ATPase
P domainP domain
Ca2+ ions
Cytosol
Asp 351A domainA domain
N domain
Mechanism:
ACTIVE TRANSPORT 2
Lactose Permease(Abramson et al., Science 2003, 301, 601)
Mechanism:
Lactose/Proton Symporter
F1F
0 ATP synthase
ATP synthase web page: http://www.atpsynthase.info/
Boyer, Annu. Rev. Biochem. 1997, 66, 717; Abrahams et al. Nature 1994, 370, 621;
Dimroth et al. EMBO Reports 2006, 7, 276
F1 ATPase
ADP + Pi + n Hout
ATP + n Hin+
+
StatorAxle
mitochondrion
ultrasound
SMP F1
membrane matrix
H+
H+ H+
Fo
F1
ATPase
ADP + Pi
ATP
ATP
synthase
NADH NAD+
a
subunit
ring of
c subunits
H+
H+
Asp61
Fo subunit c
PDB 1A91
ATP
Binding-change mechanism for ATP synthesis
repeat
ADP
+ Pi
ADP + Pi
ATP
ATP
ATP
ATP tight
binding
loose binding
open
ADP
+ Pi
Direct observation of ATP-driven rotation in ATP synthaseNoji et al. Nature 1997, 386, 299; Yasuda et al., Cell 1998, 93, 1117
actin filament
F1
Rotation of relative to &
Proton motion across the membrane drives rotation of the c ring relative to the a subunit
F1 ( )
3 subunits; the subunit, which serves as a “shaft”, is at the 3-fold axis
THE PATCH CLAMP TECHNIQUENeher & Sakmann, Sci. Am. 1992, 266, 28
By pressing a patch pipette against the enzymatically cleaned surface of a cell and applying gentle suction, researcherscan place a gigaohm seal around a small patch of membrane and the ionchannels it contains. The behavior ofthe trapped channel can be measuredupon application of various stimuli fromwithin the pipette.
Receptor channels found at the neuro-muscular end plate open in responseto the transmitter acetylcholine. Whenno acetylcholine is present, effectivelyno current passes through a channel.When acetylcholine binds to the receptor, an elementary current of afew picoamperes flows. The measureddurations of the currents and theintervals between them vary becausethe interaction of acetylcholine molecules with the receptors isgoverned by probability.
Genetically engineered frogs eggs areuseful tools for studying ion channelbehavior. RNA sequences encodingsubunits of ion channels can be injected into an egg (a). The egg willthen synthesize the channel proteinsand insert them into its surfacemembrane, where they are accessiblefor patch clamp experiments (b).
A CATION-! BINDING SITE IN THE NICOTINIC RECEPTORZhong et al., Proc. Natl. Acad. Sci. USA 1998, 95, 12088-12093
H3CN O
CH3H3CO
CH3+
Replacement of Trp149of the "-subunit
PASSIVE TRANSPORT
(from Berg, Tymoczko & Stryer, Biochemistry, 5th Ed.)
A single subunit
10 Å
34 Å
12 Å
3 Å
View down the pore
Path through the channel
Selectivityfilter
Potassium channel (Doyle et al., Science 1998, 280, 69-77)
A1 = 2-adamantanamine; A2 = 1-adamantanecarboxylic acid
STOCHASTIC SENSING OF ORGANIC ANALYTES Gu et al., Nature 1999, 398, 686-690