Announcements Homework #8 assigned today 4/19/10, due next Wednesday. Wednesday, 4/21/10: Quiz on...
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Transcript of Announcements Homework #8 assigned today 4/19/10, due next Wednesday. Wednesday, 4/21/10: Quiz on...
Announcements
Homework #8 assigned today 4/19/10, due next Wednesday.
Wednesday, 4/21/10: Quiz on reading from ECB, Nerves.
This Friday, 4/23/10: email your final topic verbal and oral presentation. Include both a write-up and PDF of the research paper. It must be on a totally different topic (technique and biology) than mid-term presentation. I will get back to you by Monday 4/26/10.
Final Paper: due evening May 5th.Final presentation—need two days (3 meetings): Monday May 3rd, Wednesday May 5th, night of Wednesday May 5th, 5pm (Pizza included.)
Final Lectures: W, April 21st; M April 26th; W April 28th
Quiz (Chpt 12, ECB)
6. Different types of stimuli influence the opening and closing of ion channels. List three classes of gated ion channels that are controlled by different stimuli: _________ ____________, ______________ and ________________.
1. Membrane transport proteins can be divided into two main classes: ___________ and ___________. The basic difference between these two classes of membrane transport proteins is the way they___________________ _______.
2. In passive transport, an uncharged solute or an ion is transported ___________its electrochemical gradient. In active transport, an uncharged solute or an ion is transported __________it concentration or electrochemical gradient in a process that requires _______________.
3. Solute transfer carried out by transporters can be ______________; transport by channels is _________________.
4. The Na+-K+ pump in the plasma membrane of animal cells is _____________ that actively transports Na+ _______of the cell and K+ ______.
5. Neurons propagate signals in the form of ______ _____________, which are usually mediated by voltage-gated ________________ that open in response to ______________of the plasma membrane
transporters channels
discriminate between solutes
down
against
energy
active or passive always passive
an ATPase out in
actionpotentials
Na+ channels depolarization
voltage-gated ligand-gated stress-activated
(Mechanosensitive)
how many different ion channels?
Ans:25-30,000 genes: 5000-6,000 genes. One or more polypeptide/ion channel– could get less, or more, ion channels.
Ion Channels
0 mV
-60 to -100 mV (closed, polarized)
0 mV (open, depolarized)
Shaker Potassium Ion Channels
Start of Action Potential
--pressure, vibration receptors, located in skin, and various internal organs (joints, tendons and tissues that lines the organs and blood vessels), connected to a sensory neuron. They are the largest of the skin's receptors and are believed to provide instant information about how and where we move.
I said Ca2+ released, e.g. by muscle. But nerve propulsion also starts by sodium inflow, largely with mechanosensitive receptors. In skin cells, mechanically-gated sodium channels.
The Pacinian Corpuscle
http://www.biologymad.com/NervousSystem/nerveimpulses.htm
Proprioception is our "body sense".
Bezanilla, 2008, Nature Reviews
Potassium & Sodium Channel SimilarK+ Channel: homotetramer S1-S6
Na+ Channel heterotetramer S1-S6: with each sub-unit havingslight variations)
K+S5
S6S4
S3S2
S1
X-ray Crystal Structure
K+S5
S6S4
S3S2
S1
Structure of Pore-Domain(S5-S6) is known
(KvAP, Kv1.2… all yield the same structure)
¼ of aKV channel(1 -subunit)
aS1 S2 S3 S4 S5 P S6
S1 S1S4 S4
S2 S2S3 S3
+++
+++
S5 S5S6 S6
b Voltage-sensingdomains (S1-S4)
surround the pore-domain (S5-S6)
Pore figure adapted fromJiang, Y. et al. Nature 417, 523-6. (2002).
But how S4 (and S1-S3) move, remain controversial.
Explains ion selectivity (K+ > Na+) and rapid ion flux.
Excellent agreement between LRET/FRET and Crystallography
Rod MacKinnon won Nobel Prize
Notice Selectivity Filter (GYG)
If 10,000 fold selectivity, what is ENa vs. EK ?
Ans: 9.2kT
Hydration Energy
Sodium channel been crystallized. C=O just right for Na+.
Inside Outside
Point mutation in Potassium Gene that affects Potassium
Channel
How does gate turn on/shut off?
K+
K+
Open
K+
-0.1 V
Outside
ClosedHigh K+(Low Na+)
Low K+(High Na+)
0 V
0 mV
+ + +
+ + +K+
S5S6
S4S3
S2S1
How does gate (S4) move? General Models
Piston?
Paddle?
Jiang et al.Nature, 2003
RoderickMacKinnon
Blaustein and Miller, Nature 427, 499-500. (2004).
Voltage-DrivenHelicalScrew
++
+
++
++
-
++
++
++
+-
a.
Voltage-DrivenCreviceShaping
++
+
++
++
++
+
++
++
--
No Translation, No Rotationb.
c.
S4
S4
S4 S4
gatin
g ca
nal
gatin
g ca
nal
gatin
g ca
nal
gatin
g ca
nal
Pure Rotation
Resting
S4 S4
Rotation?
Cork-screw?
Crevice Reshaping?
LRET using stationary toxins
-150 -100 -50 0 50 10030
31
32
33
34
35
36
-150 -100 -50 0 5030
31
32
33
34
35
36
-150 -100 -50 0 5015
20
25
30
35S4
Aver
age
dist
ance
s (a
ngst
rom
s) S
4
Voltage (mV)
R365C BodipyFl-CTXD = -0.8 angstromsn = 7
L361C BodipyFl-AgTXD = -0.7 angstromsn = 8
L361C BodipyFl-CTXD = -0.7 angstromsn = 8
S3b
E335C BodipyFl-CTXD = 0.7 angstromsn = 3
E335C BodipyFl-AgTXD = 1.1 angstromsn = 5
E333C BodipyFl-CTXD = 0.8 angstromsn = 13
V330C BodipyFl-CTXD = 0.1 angstromsn = 11
Ave
rage
dis
tanc
es (a
ngst
rom
s) S
3b
Voltage (mV)
S346C lucifer yellow-CTXD = 0.7 angstromsn = 6
S346C Atto465-CTXD = 0.5 angstromsn = 6
S351C Atto465-CTXD = -2.3 angstromsn = 17
S351C BodipyFl-CTXD = -2.4 angstromsn = 16
S352C BodipyFl-CTXD = -1.7 angstromsn = 5
N353C BodipyFl-CTXD = -2.0 angstromsn = 5
N353C BodipyFl-AgTXD = -1.4 angstromsn = 4
S3-S4 linker
Ave
rage
dis
tanc
es (a
ngst
rom
s) S
3-S
4 lin
ker
Voltage (mV)
-150 -100 -50 0 50 10030
31
32
33
34
35
36
-150 -100 -50 0 5030
31
32
33
34
35
36
-150 -100 -50 0 5015
20
25
30
35S4
Aver
age
dist
ance
s (a
ngst
rom
s) S
4
Voltage (mV)
R365C BodipyFl-CTXD = -0.8 angstromsn = 7
L361C BodipyFl-AgTXD = -0.7 angstromsn = 8
L361C BodipyFl-CTXD = -0.7 angstromsn = 8
S3b
E335C BodipyFl-CTXD = 0.7 angstromsn = 3
E335C BodipyFl-AgTXD = 1.1 angstromsn = 5
E333C BodipyFl-CTXD = 0.8 angstromsn = 13
V330C BodipyFl-CTXD = 0.1 angstromsn = 11
Aver
age
dist
ance
s (a
ngst
rom
s) S
3b
Voltage (mV)
S346C lucifer yellow-CTXD = 0.7 angstromsn = 6
S346C Atto465-CTXD = 0.5 angstromsn = 6
S351C Atto465-CTXD = -2.3 angstromsn = 17
S351C BodipyFl-CTXD = -2.4 angstromsn = 16
S352C BodipyFl-CTXD = -1.7 angstromsn = 5
N353C BodipyFl-CTXD = -2.0 angstromsn = 5
N353C BodipyFl-AgTXD = -1.4 angstromsn = 4
S3-S4 linker
Ave
rage
dis
tanc
es (a
ngst
rom
s) S
3-S
4 lin
ker
Voltage (mV)
-150 -100 -50 0 50 10030
31
32
33
34
35
36
-150 -100 -50 0 5030
31
32
33
34
35
36
-150 -100 -50 0 5015
20
25
30
35S4
Ave
rage
dis
tanc
es (a
ngst
rom
s) S
4
Voltage (mV)
R365C BodipyFl-CTXD = -0.8 angstromsn = 7
L361C BodipyFl-AgTXD = -0.7 angstromsn = 8
L361C BodipyFl-CTXD = -0.7 angstromsn = 8
S3b
E335C BodipyFl-CTXD = 0.7 angstromsn = 3
E335C BodipyFl-AgTXD = 1.1 angstromsn = 5
E333C BodipyFl-CTXD = 0.8 angstromsn = 13
V330C BodipyFl-CTXD = 0.1 angstromsn = 11
Aver
age
dist
ance
s (a
ngst
rom
s) S
3b
Voltage (mV)
S346C lucifer yellow-CTXD = 0.7 angstromsn = 6
S346C Atto465-CTXD = 0.5 angstromsn = 6
S351C Atto465-CTXD = -2.3 angstromsn = 17
S351C BodipyFl-CTXD = -2.4 angstromsn = 16
S352C BodipyFl-CTXD = -1.7 angstromsn = 5
N353C BodipyFl-CTXD = -2.0 angstromsn = 5
N353C BodipyFl-AgTXD = -1.4 angstromsn = 4
S3-S4 linker
Ave
rage
dis
tanc
es (a
ngst
rom
s) S
3-S
4 lin
ker
Voltage (mV)
Only 2Å change! Not much change
MacKinnonModel
Not translation model.We believe rotation model.
Class evaluation
1. What was the most interesting thing you learned in class today?
2. What are you confused about?
3. Related to today’s subject, what would you like to know more about?
4. Any helpful comments.
Answer, and turn in at the end of class.