9. Ion flow Fain Chapter 3 part 1 9/30/09. Homework - rhodopsin seqs.

9. Ion flow9. Ion flow

Fain Chapter 3 part 19/30/09

Homework - rhodopsin seqsHomework - rhodopsin seqs

Human_rho MNGTEGPNFYVPFSNATGVVRSPFEYPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYChimp_rho MNGTEGPNFYVPFSNATGVVRSPFEYPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYDog_rho MNGTEGPNFYVPFSNKTGVVRSPFEYPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYMouse_rho MNGTEGPNFYVPFSNVTGVVRSPFEQPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYRat_rho MNGTEGPNFYVPFSNITGVVRSPFEQPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYCow_rho MNGTEGPNFYVPFSNKTGVVRSPFEAPQYYLAEPWQFSMLAAYMFLLIMLGFPINFLTLYZfish_rho MNGTEGPAFYVPMSNATGVVRSPYEYPQYYLVAPWAYGFVAAYMFFLIITGFPVNFLTLYChick_rho MNGTEGINFYVPMSNKTGVVRSPFEYPQYYLAEPWKYRLVCCYIFFLISTGLPINLLTLL ****** ****:** *******:* *****. ** : ::..*:*:** *:*:*:*** 23 variable Human_rho VTVQHKKLRTPLNYILLNLAVADLFMVLGGFTSTLYTSLHGYFVFGPTGCNLEGFFATLGChimp_rho VTVQHKKLRTPLNYILLNLAVADLFMVLGGFTSTLYTSLHGYFVFGPTGCNLEGFFATLGDog_rho VTVQHKKLRTPLNYILLNLAVADLFMVFGGFTTTLYTSLHGYFVFGPTGCNVEGFFATLGMouse_rho VTVQHKKLRTPLNYILLNLAVADLFMVFGGFTTTLYTSLHGYFVFGPTGCNLEGFFATLGRat_rho VTVQHKKLRTPLNYILLNLAVADLFMVFGGFTTTLYTSLHGYFVFGPTGCNLEGFFATLGCow_rho VTVQHKKLRTPLNYILLNLAVADLFMVFGGFTTTLYTSLHGYFVFGPTGCNLEGFFATLGZfish_rho VTIEHKKLRTPLNYILLNLAIADLFMVFGGFTTTMYTSLHGYFVFGRLGCNLEGFFATLGChick_rho VTFKHKKLRQPLNYILVNLAVADLFMACFGFTVTFYTAWNGYFVFGPVGCAVEGFFATLG **.:***** ******:***:*****. *** *:**: :****** ** :******** 17

Human_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLAGWS----Chimp_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLAGWS----Dog_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLAGWSSLLSMouse_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVVFTWIMALACAAPPLVGWS----Rat_rho GEIGLWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLVGWS----Cow_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLVGWS----Zfish_rho GEMGLKSLVVLAIERWMVVCKPVSNFRFGENHAIMGVAFTWVMACSCAVPPLVGWS----Chick_rho GQVALWSLVVLAIERYIVVCKPMGNFRFSATHAMMGIAFTWVMAFSCAAPPLFGWS---- *::.* *********::*****:.****. .**:**:.***:** :**.*** *** 23

Human_rho ------RYIPEGLQCSCGIDYYTLKPEVNNESFVIYMFVVHFTIPMIIIFFCYGQLVFTVChimp_rho ------RYIPEGLQCSCGIDYYTLKPEVNNESFVIYMFVVHFTIPMIIIFFCYGQLVFTVDog_rho HSPLVLRYIPEGMQCSCGIDYYTLKPEINNESFVIYMFVVHFAIPMIVIFFCYGQLVFTVMouse_rho ------RYIPEGMQCSCGIDYYTLKPEVNNESFVIYMFVVHFTIPMIVIFFCYGQLVFTVRat_rho ------RYIPEGMQCSCGIDYYTLKPEVNNESFVIYMFVVHFTIPMIVIFFCYGQLVFTVCow_rho ------RYIPEGMQCSCGIDYYTPHEETNNESFVIYMFVVHFIIPLIVIFFCYGQLVFTVZfish_rho ------RYIPEGMQCSCGVDYYTRTPGVNNESFVIYMFIVHFFIPLIVIFFCYGRLVCTVChick_rho ------RYMPEGMQCSCGPDYYTHNPDYHNESYVLYMFVIHFIIPVVVIFFSYGRLICKV **:***:***** **** :***:*:***::** **:::***.**:*: .* 28

Human_rho KEAAAQQQESATTQKAEKEVTRMVIIMVIAFLICWVPYASVAFYIFTHQGSNFGPIFMTIChimp_rho KEAAAQQQESATTQKAEKEVTRMVIIMVIAFLICWVPYASVAFYIFTHQGSNFGPIFMTIDog_rho KEAAAQQQESATTQKAEKEVTRMVIIMVIAFLICWVPYASVAFYIFTHQGSDFGPIFMTLMouse_rho KEAAAQQQESATTQKAEKEVTRMVIIMVIFFLICWLPYASVAFYIFTHQGSNFGPIFMTLRat_rho KEAAAQQQESATTQKAEKEVTRMVIIMVIFFLICWLPYASVAMYIFTHQGSNFGPIFMTLCow_rho KEAAAQQQESATTQKAEKEVTRMVIIMVIAFLICWLPYAGVAFYIFTHQGSDFGPIFMTIZfish_rho KEAARQQQESETTQRAEREVTRMVIIMVIAFLICWLPYAGVAWYIFTHQGSEFGPVFMTLChick_rho REAAAQQQESATTQKAEKEVTRMVILMVLGFMLAWTPYAVVAFWIFTNKGADFTATLMAV :*** ***** ***:**:*******:**: *::.* *** ** :***::*::* . :*:: 25

Human_rho PAFFAKSAAIYNPVIYIMMNKQFRNCMLTTICCGKNPLGDDE--ASATVSKTETSQVAPAChimp_rho PAFFAKSAAIYNPVIYIMMNKQFRNCMLTTICCGKNPLGDDE--ASATVSKTETSQVAPADog_rho PAFFAKSSSIYNPVIYIMMNKQFRNCMITTLCCGKNPLGDDE--ASASASKTETSQVAPAMouse_rho PAFFAKSSSIYNPVIYIMLNKQFRNCMLTTLCCGKNPLGDDD--ASATASKTETSQVAPARat_rho PAFFAKTASIYNPIIYIMMNKQFRNCMLTTLCCGKNPLGDDE--ASATASKTETSQVAPACow_rho PAFFAKTSAVYNPVIYIMMNKQFRNCMVTTLCCGKNPLGDDE--ASTTVSKTETSQVAPAZfish_rho PAFFAKTSAVYNPCIYICMNKQFRHCMITTLCCGKNPFEEEEG-ASTTASKTEASSVSSSChick_rho PAFFSKSSSLYNPIIYVLMNKQFRNCMITTICCGKNPFGDEDVSSTVSQSKTEVSSVSSS ****:*::::*** **: :*****:**:**:******: ::: ::.: ****.*.*:.: 29

Human_rho -----Chimp_rho -----Dog_rho -----Mouse_rho -----Rat_rho -----Cow_rho -----Zfish_rho SVSPAChick_rho QVSPA 5

Total sites = 6*60 + 5 -= 365

Variable = 150

Fixed = 215 / 365 = 58.9%

Protein interactionsProtein interactions

Rhodopsin

GNAT1

GNB1

GNGT1

G protein kinaseArrestin

Protdist - pairwise distancesProtdist - pairwise distances

Distance = difference btn 2 sequences = 1 - fraction of fixed sites

HW - dist matrix for RhoHW - dist matrix for Rho

8

Human_rho 0.00000 0.00001 0.04769 0.05420 0.05186 0.07040 0.242057 0.38324

Chimp_rho 0.00001 0.00000 0.04769 0.05420 0.05186 0.07040 0.24206 0.38324

Dog_rho 0.04769 0.04769 0.00000 0.04525 0.04846 0.06124 0.22672 0.34926

Mouse_rho 0.05419 0.05420 0.04525 0.00000 0.02969 0.07087 0.23692 0.38622

Rat_rho 0.05185 0.05185 0.04846 0.02969 0.00000 0.06790 0.22196 0.39169

Cow_rho 0.07040 0.07040 0.06124 0.07087 0.06790 0.00000 0.21113 0.37531

Zfish_rho 0.24206 0.24206 0.22672 0.23692 0.22196 0.21113 0.00000 0.41065

Chick_rho 0.38324 0.38324 0.34926 0.38622 0.39170 0.37531 0.41065 0.00000

Homework - dist matrix for Homework - dist matrix for RhoRho

8 Human Chimp Dog Mouse Rat Cow Zfish Chick

Human_rho 0.00000 0.00001 0.04769 0.05420 0.05186 0.07040 0.242057 0.38324

Chimp_rho 0.00001 0.00000 0.04769 0.05420 0.05186 0.07040 0.24206 0.38324

Dog_rho 0.04769 0.04769 0.00000 0.04525 0.04846 0.06124 0.22672 0.34926

Mouse_rho 0.05419 0.05420 0.04525 0.00000 0.02969 0.07087 0.23692 0.38622

Rat_rho 0.05185 0.05185 0.04846 0.02969 0.00000 0.06790 0.22196 0.39169

Cow_rho 0.07040 0.07040 0.06124 0.07087 0.06790 0.00000 0.21113 0.37531

Zfish_rho 0.24206 0.24206 0.22672 0.23692 0.22196 0.21113 0.00000 0.41065

Chick_rho 0.38324 0.38324 0.34926 0.38622 0.39170 0.37531 0.41065 0.00000

Distances are fraction of sites which differ

Small distance means small difference = high similarity

Trifurcating tree

Can reroot

Zebrafish makes the most sense as the root.

Is this the tree you expect?

ParsimonyParsimonyTrees joined in different ways are just as likely based on # of changes

Distance and ML trees are similar Distance and ML trees are similar but not identicalbut not identical

Distance

Max likelihood

oooooooooooooooooooooooooooooooooooooooooooooooooooooooooo --- PhyML v3.0 ---

A simple, fast, and accurate algorithm to estimate large phylogenies

by maximum likelihood Stephane Guindon & Olivier Gascuel

http://atgc.lirmm.fr/phyml

Copyright CNRS - Universite Montpellier II

ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo. Sequence file : Rho.phylipi. Data set : #1. Tree search : NNIs. Initial tree : BIONJ. Model of amino acids substitution : LG. Number of taxa : 8. Log-likelihood : -2100.30553. Discrete gamma model : No. Time used 0h0m5s oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooLog-likelihood is a statistic which tells you how

good the tree is : more negative is better

What did we learn from all What did we learn from all this?this?

Distance is fast Parsimony gives us too many trees

and no similarity info ML is best - provides confidence

on resultsBut it can take forever

Human_rho MNGTEGPNFYVPFSNATGVVRSPFEYPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYChimp_rho MNGTEGPNFYVPFSNATGVVRSPFEYPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYDog_rho MNGTEGPNFYVPFSNKTGVVRSPFEYPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYMouse_rho MNGTEGPNFYVPFSNVTGVVRSPFEQPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYRat_rho MNGTEGPNFYVPFSNITGVVRSPFEQPQYYLAEPWQFSMLAAYMFLLIVLGFPINFLTLYCow_rho MNGTEGPNFYVPFSNKTGVVRSPFEAPQYYLAEPWQFSMLAAYMFLLIMLGFPINFLTLYZfish_rho MNGTEGPAFYVPMSNATGVVRSPYEYPQYYLVAPWAYGFVAAYMFFLIITGFPVNFLTLYChick_rho MNGTEGINFYVPMSNKTGVVRSPFEYPQYYLAEPWKYRLVCCYIFFLISTGLPINLLTLL ****** ****:** *******:* *****. ** : ::..*:*:** *:*:*:*** 23 variable Human_rho VTVQHKKLRTPLNYILLNLAVADLFMVLGGFTSTLYTSLHGYFVFGPTGCNLEGFFATLGChimp_rho VTVQHKKLRTPLNYILLNLAVADLFMVLGGFTSTLYTSLHGYFVFGPTGCNLEGFFATLGDog_rho VTVQHKKLRTPLNYILLNLAVADLFMVFGGFTTTLYTSLHGYFVFGPTGCNVEGFFATLGMouse_rho VTVQHKKLRTPLNYILLNLAVADLFMVFGGFTTTLYTSLHGYFVFGPTGCNLEGFFATLGRat_rho VTVQHKKLRTPLNYILLNLAVADLFMVFGGFTTTLYTSLHGYFVFGPTGCNLEGFFATLGCow_rho VTVQHKKLRTPLNYILLNLAVADLFMVFGGFTTTLYTSLHGYFVFGPTGCNLEGFFATLGZfish_rho VTIEHKKLRTPLNYILLNLAIADLFMVFGGFTTTMYTSLHGYFVFGRLGCNLEGFFATLGChick_rho VTFKHKKLRQPLNYILVNLAVADLFMACFGFTVTFYTAWNGYFVFGPVGCAVEGFFATLG **.:***** ******:***:*****. *** *:**: :****** ** :******** 17

Human_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLAGWS----Chimp_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLAGWS----Dog_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLAGWSSLLSMouse_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVVFTWIMALACAAPPLVGWS----Rat_rho GEIGLWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLVGWS----Cow_rho GEIALWSLVVLAIERYVVVCKPMSNFRFGENHAIMGVAFTWVMALACAAPPLVGWS----Zfish_rho GEMGLKSLVVLAIERWMVVCKPVSNFRFGENHAIMGVAFTWVMACSCAVPPLVGWS----Chick_rho GQVALWSLVVLAIERYIVVCKPMGNFRFSATHAMMGIAFTWVMAFSCAAPPLFGWS---- *::.* *********::*****:.****. .**:**:.***:** :**.*** *** 23

Human_rho ------RYIPEGLQCSCGIDYYTLKPEVNNESFVIYMFVVHFTIPMIIIFFCYGQLVFTVChimp_rho ------RYIPEGLQCSCGIDYYTLKPEVNNESFVIYMFVVHFTIPMIIIFFCYGQLVFTVDog_rho HSPLVLRYIPEGMQCSCGIDYYTLKPEINNESFVIYMFVVHFAIPMIVIFFCYGQLVFTVMouse_rho ------RYIPEGMQCSCGIDYYTLKPEVNNESFVIYMFVVHFTIPMIVIFFCYGQLVFTVRat_rho ------RYIPEGMQCSCGIDYYTLKPEVNNESFVIYMFVVHFTIPMIVIFFCYGQLVFTVCow_rho ------RYIPEGMQCSCGIDYYTPHEETNNESFVIYMFVVHFIIPLIVIFFCYGQLVFTVZfish_rho ------RYIPEGMQCSCGVDYYTRTPGVNNESFVIYMFIVHFFIPLIVIFFCYGRLVCTVChick_rho ------RYMPEGMQCSCGPDYYTHNPDYHNESYVLYMFVIHFIIPVVVIFFSYGRLICKV **:***:***** **** :***:*:***::** **:::***.**:*: .* 28

Funky dog sequence- predicted from genome

GNB (GNB ( subunit of G protein transducin) subunit of G protein transducin)

Rod

Cone

Cone cladeCone clade

Rod cladeRod cladeA

B

Key steps of sensory Key steps of sensory transductiontransduction

1. Stimulus is received2. Changes confirmation of receptor

molecule3. Causes change in membrane

potential4. Changes neural output

Change in membrane Change in membrane potentialpotential

To change membrane potential, need to get ions to flow

Two ways for ions to flowIon channel

Passive flow - diffusionIon pump

Active flow - uses energy

QuestionsQuestions

1. How do ion channels obtain specificity?

2. How do ion pumps differ?3. How are membrane potential and

ion concentration related?What does that tell us about

mechanism?

Ion channelIon channel

Integral to membraneEmbedded in hydrophobic

environmentTraverses one side of membrane to the

other Comprised of several protein

subunitsHomodimer - same subunitsHeterodimer - different subunits

Ion channelIon channel

Has a special region that forms a pore or channel

Conducts one type of ionSize specificIon flow through channel is very fast

Pore is gatedCan be either closed or openConformational change - move AA

which normally occlude opening

Shaker potassium channelShaker potassium channel

Discovered in Drosophila melanogasterShake legs when

anaesthetized with ether

Identified mutation in gene for subunit of an ion channelSelective for K+

Papazain et al 1987Temple et al 1987

subunit of channelsubunit of channel

Fain fig 3.1a

Pore regionPore region

Fain 3.1b

How ion channels workHow ion channels work

Nobel prize for Chemistry 2003Roderick Mackinnon, Rockefeller Univ

X ray crystal structure of X ray crystal structure of bacterial channelbacterial channel

K+ channel from Streptomyces lividans (simple channel)

Channel has 6 TM + 1 P Channel has 6 TM + 1 P regionregion

4 subunitsper channel

P region is highly conservedP region is highly conserved

Conformational change when Conformational change when channel openschannel opens

Voltage gated

Pore regions are right in the Pore regions are right in the middle of the channelmiddle of the channel

KK++ enters as hydrated ion enters as hydrated ion

KK++ sheds water and sheds water and coordinates with COOcoordinates with COO--

groupsgroups

4 possible binding sites

Selectivity: KSelectivity: K++ is necessary is necessary for stable channel structurefor stable channel structure

Selectivity for K+ / Na+ = 10,000

High Naconcentration

4 sites - 2 ions bind4 sites - 2 ions bind

Channels are gatedChannels are gated

Voltage gated - ion specificNa+ K+ Ca+2 Cl-

Ca+2 activated Cyclic nucleotide gated - cAMP,

cGMP Ligand gated - acetylcholine,

glutamate Light gated Stretch gated

Voltage gating - charged AA Voltage gating - charged AA in membrane movein membrane move

Fig 3.3a

Types of channelsTypes of channels

Ionotropic Signal from outside cellVoltage, stretch, ligand

MetabotropicSignal from inside cellLigandModifier (Ca)

Fig 3.3

Voltage gated

Ligand gated - extracellular

cGMP - intracellular

Ionotropic channelsIonotropic channels

Channel is the receptorDetects deformation or change in

pressure Important in

Mechanoreceptors of skinStretch receptors in muscleHair cells in vestibular system and ear

Stretch activated channelsStretch activated channels

Fig 3.4

0

Patch of membrane also Patch of membrane also responds to pressureresponds to pressure

Ionotropic - doesn’t need inside of cell to respond so not metabotropic

Fain 3.4b

Channels Channels

Channels allow ions to move down concentration gradient

Channels vs pumpsChannels vs pumps

Ion pumps move ions against concentration gradients - use energy

Ion pumps - NaIon pumps - Na++/K/K++ ATPase ATPase

Fain 3.7a

Two subunits - subunit binds ions

Sodium pumpSodium pump

Cell interior


3Na+

Fain 3.7b


3Na+ pumped out

2K+ pumped in

Fain 3.7b

Ion pump creates a concentration Ion pump creates a concentration gradient across cell membranegradient across cell membrane

Na/K ATPase

Outside cell Inside cell

Na+

Na+

Na+

Na+

Na+

Na+

Na+

Na+

Na+

K+

K+

K+

K+

K+

K+

K+

K+

K+

K+

K+

K+

K+

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

Cl-

K+

32

Membrane potentialsMembrane potentials

Ion flow sets up concentration gradients

Ion concentrations determine voltage or potential across cell membrane

Changes in membrane potential are signals produced by sensory cells

Communicated to central nervous system (Action potentials)

Ion pump creates a concentration Ion pump creates a concentration gradient across cell membranegradient across cell membrane

Na/K ATPase


Na+

K+

Cl-

10-20 mM

5-10 mM

120-140 mM

Na+

K+

Cl-

141 mM

124 mM

3.3 mM

Membrane potentialMembrane potential

When channels are open, there will be a balance of diffusion and electrostatics

-------

K+ K+ Concentration

Charge

Mass and charge make K+ move in opposite directions

Walther NernstWalther Nernst

Won Nobel prize in chemistry in 1920

Original “Nernst equation” was written for electrochemistry

Personification of Nernst Personification of Nernst equation - students in a equation - students in a

classroomclassroom

Students will move out until Students will move out until same density in and outsame density in and out

If there are a few hot fudge If there are a few hot fudge sundaes…sundaes…

Might get few students coming back in

If there are lots of sundaes…If there are lots of sundaes…

Everyone who wants one will come back in

Nernst equationNernst equation

At equilibrium, can determine membrane potential which offsets ion gradient across membrane

€

Vm =RT

zFlnKoK i

Vm =59mV

zlogKoK i

-------

K+ K+

Vm

Ko - outsideKi - inside

+++++++++

Membrane potential increases till Membrane potential increases till there is equilibriumthere is equilibrium


120 mMNa/K ATPase

K+ K+3.3 mM

€

Vm = 59mV (log(3.3

120) = −92mV

-----------

++++++++++

Actual membranes involve transfer Actual membranes involve transfer of several ionsof several ions

Na/K ATPase


Na+

K+

Cl-

15 mM

5 mM

120 mM

Na+

K+

Cl-

141 mM

124 mM

3.3 mM

Goldman voltage equation Goldman voltage equation consider multiple ionsconsider multiple ions

For both Na and K

If is ratio of permeabilities: PNa/PK

€

Vm =RT

FlnαNao +KoαNai +K i

€

Vm =RT

FlnPNaNao + PKKoPNaNai + PKK i

For a K selective channel, = 0.02

Membrane potential is less when Membrane potential is less when consider both Naconsider both Na++ and K and K++

Na/K ATPase


Na+

K+

15 mM

120 mM

Na+

K+

141 mM

3.3 mM

€

Vm = 59mV ln0.02*141+ 3.3mM

0.02*15 +120mM= −78mV

This is close to actual membrane potential measured in olfactory receptor

Typical cellsTypical cells

Variation in Na permeabilityChanges resting membrane potential

-35 mV to -90 mVAlways negative inside cell

Sometimes need to include Ca+2 or Cl-

Na+/Ca+2 ATPase

Ion channels perturb steady Ion channels perturb steady state membrane potentialstate membrane potential

Opening of channels lets ions flowPositive ions flow in to negative cell :

Na+ Ions in high concentration outside cell

flow in : Na+ Na+ flowing in makes cell less

negativeDepolarizes

Depolarization - become less Depolarization - become less polarized; potential gets polarized; potential gets

smallersmaller

-75mV

-35 mV

stimulus

+ Ion flow into cell

Membrane potential decreases

0 V

Vm

QuestionsQuestions

1. How do ion channels obtain specificity?

2. How do ion pumps differ?3. How are membrane potential and

ion concentration related?What does that tell us about

mechanism?

Next week is Nobel weekNext week is Nobel week

Many Nobel prizes have been awarded for work in sensory systems or genetics

See class web site for links

9. Ion flow Fain Chapter 3 part 1 9/30/09. Homework - rhodopsin seqs.

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Transcript of 9. Ion flow Fain Chapter 3 part 1 9/30/09. Homework - rhodopsin seqs.