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

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


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


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)




S3b





Aver

age

dist

ance

s (a

ngst

rom

s) S

3b

Voltage (mV)








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)




S3b





Aver

age

dist

ance

s (a

ngst

rom

s) S

3b

Voltage (mV)








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.

Documents

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