Molecular Switches - biochemie.lw.uni-leipzig.de · MOLECULAR SWITCHES Institut für Biochemie OPTOCHEMICAL GENETICS 13 Photochromic ligand approach (PCL) Photoswitched tethered ligand

Molecular Switches

Grasse Nico

Mohr Alexander

MOLECULAR SWITCHES

Institut für Biochemie 2

Molecular Switches

Riboswitches

Peptide-DNA/RNA

Conjugates

Light-induced Switches

for example …

MOLECULAR SWITCHES


Molecular Switches

Riboswitches

Peptide-DNA/RNA

Conjugates


MOLECULAR SWITCHES

Institut für Biochemie

CHANGES IN BINDING AFFINITY VIA DNA/RNA HYBRIDIZATION

Röglin, L.; Altenbrunn, F.; Seitz, O.: DNA and RNA-

Controlled Switching of Protein Kinase Activity. 2009,

ChemBioChem 4

1. Src Kinase stays inactive because the

conformation of the peptide doesn’t allow a high

binding affinity

2. r969 replaces d606

3. Layed-out conformation of the peptide allows

a high affinity binding

MOLECULAR SWITCHES


CHANGES IN BINDING AFFINITY VIA DNA/RNA HYBRIDIZATION

Röglin, L.; Altenbrunn, F.; Seitz, O.: DNA and RNA-

Controlled Switching of Protein Kinase Activity. 2009,

ChemBioChem 5

Reactivation of Src

MOLECULAR SWITCHES


Molecular Switches

Riboswitches

Peptide-DNA/RNA

Conjugates


MOLECULAR SWITCHES


RIBOSWITCHES REGULATE TRANSLATION UPON LIGAND BINDING

Schwalbe, H., Buck, J., Fürtig, B., Noeske, J., Wöhnert, J.: Structures

of RNA Switches: Insight into Molecular Recognition and Tertiary

Structure. 2007, Angew. Chem.7

adenine riboswitch

guanine riboswitch

on-switch

off-switch

GlcN6P riboswitch

down-regulation of glmS

MOLECULAR SWITCHES


Molecular Switches

Riboswitches

Peptide-DNA/RNA

Conjugates


MOLECULAR SWITCHES


TYPICAL STRATEGIES FOR PHOTOSENSITIVE LIGHT-SWITCHES

Caged Ligand (CL)

Photochromic Ligand (PCL)

Photoswitchable Tetherd

Ligand (PTL)

Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical

Genetics. 2011, Angew. Chem.9

MOLECULAR SWITCHES


CLS A BIT DIFFERENT… CAGED PEPTIDE BACKBONE

The ester bond destabilizes the

tertiary structure of SDF-1α and thus

inhibits its function

The cleavage of Nvoc at 365 nm

allows an O N shift which restores

the normal backbone structure

Chemotactic potential was restored

10

Baumann, L., Beck-Sickinger, A.G.:

Photoactivatable Chemokines – Controlling Protein

Activity by Light. 2013, Angew. Chem.

Photoswitches - Applications

OPTOCHEMICAL

GENETICS

MOLECULAR SWITCHES


OPTOCHEMICAL GENETICS

aim: to persuade endogenous receptors to become sensitive toward light

3 approaches: CL, PCL, PTL

Challenge: control neural activity light responsive synthetic molecules

Focus on PCL and PTL

12

MOLECULAR SWITCHES


OPTOCHEMICAL GENETICS

13

Photochromic ligand approach (PCL)Photoswitched tethered ligand approach

(PTL)

- Azobenzenes as photoswitchable

components!

Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,

Angew. Chem.

Bioconjugation of

engineered Cys-residues

MOLECULAR SWITCHES


BIOCONJUGATION STRATEGIES FOR CYSTEIN RESIDUES

14

• free Cys rarely occurs on protein

surface

Chemoselective modification

MOLECULAR SWITCHES


AZOBENZENES

15Rau, H. (1990). Rabek, J. F. (ed.). Photochemistry and Photophysics. 2. Boca

Raton, FL: CRC Press. pp. 119–141.

MOLECULAR SWITCHES


SYNTHESIS OF AZOBENZENES

16

A: reduction of nitrobenzene

with NaHgx or LiAlH4

B: oxidation of hyrazobenzene

with NaOBr

C: condensation of

nitrosobenzene with aniline

(acidic conditions)

The preparation of some cis-azo-compounds in J. Chem. Soc. 1938, S. 876–881.

MOLECULAR SWITCHES


PCL PTL

Advantages - easy to synthesize

- easy application

- fast distribution in

tissue

• high selectivity

• ligand covalently

attached to receptor

affinity of ligand

is not major

concern

Disadvantages - low selectivity

- photoisomers show

relatively small

efficiacy

- needs high affinity

ligands

- photoswitch must

be coupled to

receptor covalently

- genetic

modification of

receptor


Angew. Chem.

MOLECULAR SWITCHES


VOLTAGE-GATED POTASSIUM CHANNELS

18

1) the transmembrane potential of aneuron at rest

2) a neurotransmitter binds to a ligand-gated ionchannel and evokes an excitatory postsynapticpotential

3) voltage-gated sodium channels (NaV)respond and further depolarize the membrane

4) voltage-gated potassium channels (KV) follow suitand repolarize the membrane

6) the undershoot (5) is removed through theconcerted action of channels that are open at theresting potential and by ATP-driven ion pumps


Angew. Chem.

MOLECULAR SWITCHES


PHOTOSENSITIZING VOLTAGE-GATED POTASSIUM CHANNELS

19

• blockers are covalently attachted to

corresponding receptors via PTL

approach

Switchable blocking and activation

of voltag-gated ion channels


Angew. Chem.

MOLECULAR SWITCHES


EXPERIMENTAL DATA

20

- Reversible light control ofpotassium currents

- Irradiation in the UV rangeunblocks channels

- 500 nm light induces blocking


Angew. Chem.

MOLECULAR SWITCHES


PHOTOSENSITIZING IONOTROPIC GLUTAMATE RECEPTORS

Glutamate receptors play important role in synaptic transmission

Located in primary postsynaptic membranes

Glutamate released from vesicles on presynaptic side

Glutamate binding leads to depolarizing current exciatory postsynaptic

potential

Important for neuronal communication associated with neuronal diseases,

e.g. Alzheimer, epilepsy ...

21Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,

Angew. Chem.

MOLECULAR SWITCHES



• Unspecific for Na+/K+-cations

• various agonists

• also Ca2+ channels


Angew. Chem.

MOLECULAR SWITCHES




Angew. Chem.

MOLECULAR SWITCHES


... ALSO VIA PCL APPROACH


Angew. Chem.

MOLECULAR SWITCHES


OUTLOOK

Same principles applicable for many more Channels/Receptors if the X-ray

crystallography is available

GPCRs could be possible targets as the natural occurring photoreceptor

Rhodopsin belongs to this category

TRP Channels can be opened by switching from a nonpolar to a polar form

Photosensitized retinal ganglion cells restored the light-avoidance behavior

of blind mice

25

THANK YOU FOR

YOUR ATTENTION

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Molecular Switches - biochemie.lw.uni-leipzig.de · MOLECULAR SWITCHES Institut für Biochemie OPTOCHEMICAL GENETICS 13 Photochromic ligand approach (PCL) Photoswitched tethered ligand