Secondary structure in de novo designed
peptides induced by electrostatic
interaction with particles and membranes.
A catalytic example
1
Aim
A His15-Lys19 pair forms a catalytic
site for ester hydrolysis which is active only when the peptide is helical.
Patrik Nygren
1, Martin Lundqvist
2, Bo Liedberg
1, Klas Broo
2, Bengt-Harald Jonsson
2, Thomas Ederth
1,*1Division of Molecular Physics and 2Division of Molecular Biotechnology,
Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping, Sweden
We are interested in design principles which will enable us to design peptides that adopt a given secondary structure upon attachment to a surface. We want to use this to design peptides which...
● adopt a pre-determined secondary
structure upon attachment to a surface
● are selective to certain membranes
● induce lipid domains upon attachment ● have surface-activated function
Substrate:
Right: The catalytic efficiency (monitored via m-nitrophenol absorption), in the presence of peptide and particle, and control experiments.
General design principles
1
* E-mail: ted@ifm.liu.se
1 Lundqvist et al., Angew. Chem. 118, 8349
(2006). DOI: 10.1002/anie.200600965
For further details, see Nygren et al., Langmuir
26, 6437 (2010). DOI: 10.1021/la100027n
K19
H15
A helical wheel representation of a 28
amino acid peptide, designed to form an αααα-helix on a negatively charged surface.
Anionic particle or lipid membrane 0 10 20 30 40 50 Time (min) 0 0.01 0.02 0.03 0.04 0.05 A b s o rp ti o n @ 3 5 8 n m Peptide + particle Buffer Peptide Particles
Peptide-membrane interaction
Anionic membranes
The cationic peptides
We use large unilamellar vesicles (d ≈≈≈≈ 100 nm), composed of
Cholesterol / DOPG / DOPC
where the (anionic) DOPG content is used to control surface charge. Compared to particles,
membranes provide
● Wider range of pH-stability ● Dynamic interface
● Varied surface composition
Membrane-peptide interactions are of relevance also to
● Cell-penetrating peptides ● Antibiotic peptides
● Lipid raft targeting
The peptides R2L and R2V have similar structure, but differ in the hydrophobic position.
Both are unstructured on silica particles.
• Both peptides are random-coil in solution
• R2L peptides form αααα-helices upon attachment to negatively charged membranes, while
• R2V peptides form β-sheets
• The structure is (largely) unaffected by pH • The degree of secondary structure is
proportional to vesicle surface charge
-125 -100 -75 -50 -25 0 0 10 20 30 40 % DOPG Z e ta p o te n ti a l (m V ) pH 7 pH 9
We show how a small
change in primary structure
can change the peptide
secondary structure upon
electrostatic attachment to
a lipid bilayer membrane.
C D E F G A B Y1 E8 E15 E22 Q4 Q11 Q18 Q25 Q5 Q12 Q19 Q26 R6 R13 R20 R27 R3 R10 R17 R24 A2 A9 A16 A23 A7 A A A 14 21 28 Cationic residues to attract the surface Hydrophobic
elements for
charge shielding Negative charges to repel the surface and to adjust net charge Polar elements
for solvent interaction
Tyrosine for detection
Negatively charged surface
X = L, Leucine N O X = V, Valine N O
R2L
R2V
Summary
-6 -4 -2 0 2 4 6 8 10 190 200 210 220 230 240 250 260 Wavelength (nm) ∆ε R2L in buffer 10% DOPG + R2L 20% DOPG + R2L 40% DOPG + R2L, pH 7 40% DOPG + R2L, pH 9 -6 -4 -2 0 2 4 6 190 200 210 220 230 240 250 260 Wavelength (nm) ∆ε R2V in buffer 40% DOPG + R2V, pH 7 40% DOPG + R2V, pH 9Circular dichroism spectroscopy shows that R2L obtains an α-helix structure as it attaches to a bilayer.
R V E V R R V E V R R V E V R QQ QQ QQRV YVRQQ
}
β-strands CD shows β-sheet structure for R2V in the presence of bilayers. A suggestedβ-arrangement is included below.
S N H O O O N H2 O O NO2 C D E F G A B Y1, E8, E15, E22 Q4 Q11 Q18 Q25 Q5 Q12 Q19 Q26 R6, R13 R20, R27 R3, R10, R17, R24 X2 9 16 23 X X X X7 X14 X21 X28