Tag: Protein Design

Hyper-stable Designed Peptides and the Coming of Age for De Novo Protein Design

Small constrained peptides combine the stability of small molecule drugs with the selectivity and potency of antibody-based therapeutics. However, peptide-based therapeutics have largely remained underexplored due to the limited diversity of naturally occurring peptide scaffolds, and a lack of methods to design them rationally.  New computational design and wet lab methods developed at the Institute for Protein Design have now opened the door to rational design of a whole new world of hyper-stable drug-like peptide structures.

In an article published in Nature this week, Baker lab / IPD scientists and their collaborators describe the development of computational methods for de novo design of constrained peptides with exceptional stabilities. They used these computational methods to design 18-47 residue constrained peptides with diverse shapes and sizes. The designed peptides presented in the paper cover three broad categories:

1) genetically encodable disulfide cross-linked peptides,

2) synthetic disulfide cross-linked peptides with non-canonical sequences, and

3) cyclic peptides with non-canonical backbones and sequences.

Experimentally determined structures for these peptides are nearly identical to their design models.

ehee_peptide_bhardwaj_mulligan_bahl
EHEE Designed Peptide, Visual Illustration by Vikram Mulligan. The molecular surface is shown as a transparent blue shell, and the peptide’s backbone structure is pink. The amino acid’s side chains are white (carbon atoms), blue (nitrogen atoms) and red (oxygen atoms). The crisscrossing bonds that give the peptide its constrained, stable shape are in bright white.

By including D-amino acids (mirror images of the L-amino acids), and thus expanding the palette of building blocks, Baker lab scientists designed peptides in a sequence and structure space sampled rarely by Nature. Indeed, the article describes successful design of a cyclic 2-helix peptide of mix chirality that represents a shape beyond natural secondary- and tertiary structure.

These designed peptides also exhibit exceptional stability to thermal and chemical denaturation, and thus could serve as attractive scaffolds for design of novel peptide-based therapeutics. More broadly, development of this new computational toolkit to precisely design constrained peptides opens the door for “on-demand” development of a new generation of peptide-based therapeutics.

These and other breakthroughs in computational protein design are also covered in a Nature review article by David Baker, Po-Ssu Huang, and Scott E. Boyken entitled “The coming of age of de novo protein design”, part of special supplement on The Protein World.

Illustrations of designed peptides with different configurations of two structures: tightly wound ribbons and flat, arrow-shaped ribbons.
Illustrations of designed peptides with different configurations of two structures: tightly wound ribbons and flat, arrow-shaped ribbons.

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Funding Sources

The National Institutes of Health provided partial support for this work through grants P50 AG005136, T32-H600035., GM094597, GM090205, and HHSN272201200025C.  Additional funding was provided by The Three Dreamers.

A Computationally Designed Metalloprotein Using an Unnatural Amino Acid

Mulligan metal binder figureWhat if scientists could design proteins to capture specific metals from our environment?  The utility for cleaning up metals from waste water, soils, and our bodies could be tremendous.  Dr. Jeremy Mills and collaborators in Dr. Baker’s group at the University of Washington’s Institute for Protein Design (IPD) address this challenge in the first reported use of computational protein design software, Rosetta, to engineer a new metal binding protein (“MB-07”) which incorporates an “unnatural amino acid” (UAA) to achieve very high affinity binding to metal cations.  Learn more at this link.

Computational Design of a pH Sensitive Antibody Binder

Designed pH-dependent Fc binder (blue) exploits protonation of Histidine-433 (orange) in the Fc portion Immunoglobulin G (IgG, light cyan surface)

Purification of antibody IgG from crude serum or culture medium is required for virtually all research, diagnostic, and therapeutic antibody applications.  Researchers at the Institute for Protein Design (IPD) have used computational methods to design a new protein (called “Fc-Binder”) that is programed to bind to the constant portion of IgG (aka “Fc” region) at basic pH (8.0) but to release the IgG at slightly acidic pH (5.5).  Published on-line at PNAS (Dec. 31, 2013), the paper is entitled Computational design of a pH-sensitive IgG binding protein, co-authored by Strauch, E. – M., Fleishman S. J., & Baker D.  Learn more at this link.

Computational Protein Design To Improve Detoxification Rates Of Nerve Agents

Phosphotriesterase EngineeringV-type nerve agents are among the most toxic compounds known, and are chemically related to pesticides widespread in the environment. Using an integrated approach, described in an ACS Chemical Biology paper entitled Engineering V-type nerve agents detoxifying enzymes using computationally focused libraries, Dr. Izhack Cherny, Dr. Per Greisen, and collaborators increased the rate of nerve agent detoxification by the enzyme phosphotriesterase (PTE) by 5000-fold by redesigning the active site.   Learn more at this link.

One Small Molecule Binding Protein, One Giant Leap for Protein Design

Illustration rendering of the digoxigenin binding protein was prepared by Vikram Mulligan

Reported on-line  in Nature (Sept. 4, 2013) researchers at the Institute for Protein Design describe the use of Rosetta computer algorithms to design a protein which binds with high affinity and specificity to a small drug molecule, digoxigenin a dangerous but sometimes life saving cardiac glycoside.  Learn more at this link.