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Secondary structure in de novo designed peptides induced by electrostatic interaction with particles and membranes.

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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 attachmenthave 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-stabilityDynamic interface

Varied surface composition

Membrane-peptide interactions are of relevance also to

Cell-penetrating peptidesAntibiotic 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 9

Circular 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 suggested

β-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

References

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