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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
Institut für Biochemie 3
Molecular Switches
Riboswitches
Peptide-DNA/RNA
Conjugates
Light-induced Switches
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
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 5
Reactivation of Src
MOLECULAR SWITCHES
Institut für Biochemie 6
Molecular Switches
Riboswitches
Peptide-DNA/RNA
Conjugates
Light-induced Switches
MOLECULAR SWITCHES
Institut für Biochemie
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
Institut für Biochemie 8
Molecular Switches
Riboswitches
Peptide-DNA/RNA
Conjugates
Light-induced Switches
MOLECULAR SWITCHES
Institut für Biochemie
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
Institut für Biochemie
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
Institut für Biochemie
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
Institut für Biochemie
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
Institut für Biochemie
BIOCONJUGATION STRATEGIES FOR CYSTEIN RESIDUES
14
• free Cys rarely occurs on protein
surface
Chemoselective modification
MOLECULAR SWITCHES
Institut für Biochemie
AZOBENZENES
15Rau, H. (1990). Rabek, J. F. (ed.). Photochemistry and Photophysics. 2. Boca
Raton, FL: CRC Press. pp. 119–141.
MOLECULAR SWITCHES
Institut für Biochemie
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
Institut für Biochemie 17
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
Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,
Angew. Chem.
MOLECULAR SWITCHES
Institut für Biochemie
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
Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,
Angew. Chem.
MOLECULAR SWITCHES
Institut für Biochemie
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
Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,
Angew. Chem.
MOLECULAR SWITCHES
Institut für Biochemie
EXPERIMENTAL DATA
20
- Reversible light control ofpotassium currents
- Irradiation in the UV rangeunblocks channels
- 500 nm light induces blocking
Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,
Angew. Chem.
MOLECULAR SWITCHES
Institut für Biochemie
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
Institut für Biochemie 22
PHOTOSENSITIZING IONOTROPIC GLUTAMATE RECEPTORS
• Unspecific for Na+/K+-cations
• various agonists
• also Ca2+ channels
Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,
Angew. Chem.
MOLECULAR SWITCHES
Institut für Biochemie
PHOTOSENSITIZING IONOTROPIC GLUTAMATE RECEPTORS
23Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,
Angew. Chem.
MOLECULAR SWITCHES
Institut für Biochemie
... ALSO VIA PCL APPROACH
24Fehrentz, T., Schönberger, M., Trauner, D.: Optochemical Genetics. 2011,
Angew. Chem.
MOLECULAR SWITCHES
Institut für Biochemie
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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