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An efficient computational pipeline starting from validated peptide assemblies has been used to design two families of α-helical barrel proteins with functionalizable channels. This rationally seeded computational protein design approach delivers soluble, monomeric proteins that match the design targets accurately and with high success rates.

Higher order coiled coils with five or more helices can form α-helical barrels. Here the authors show that placing β-branched aliphatic residues along the lumen yields stable and open α-helical barrels, which is of interest for the rational design of functional proteins; whereas, the absence of β-branched side chains leads to unusual low-symmetry α-helical bundles.

Coiled-coil assemblies have served as a rich resource for testing fundamental principles of protein structure and function. A semi-empirical design strategy now yields the first parallel hexamer, which also displays an internal channel that can be manipulated to direct assembly.

A study demonstrates the rational de novo design of water-soluble assemblies constructed from long 3₁₀-helical peptides, and details their characterization by circular dichroism spectroscopy, analytical ultracentrifugation and X-ray crystallography.

Differential sensing aims to mimic senses such as taste and smell through the use of synthetic receptors. Here, the authors show that arrays of de novo designed peptide assemblies can be used as sensor components to distinguish various analytes and complex mixtures.

Phase separation is being revealed as important in many biological processes. Most attempts to mimic and deconstruct this use engineered natural proteins. Now it is shown that de novo proteins can be designed from first principles to undergo liquid–liquid phase separation in cells, with the potential to organize multi-enzyme pathways.

The kinesin-1 motor protein accesses open active and closed autoinhibited states. These states are regulated by a flexible elbow within a complex coiled-coil architecture. Now, a conformational switch has been developed by engineering the elbow to create a closed state that can be controllably opened with a de novo designed peptide to increase kinesin transport inside cells.

The de novo design of a pair of complementary peptides, one basic for cell penetration and target binding and one acidic that can be fused to proteins of interest, provides an approach for delivery into mammalian cells and subcellular targeting.

A series of designed peptides call the sphere of influence of the helix macrodipole into question, showing that the favorable rotamers allowed by K→E hydrogen bonds beat out the entropically penalized but macrodipole-aligned E→K hydrogen bonds.

The ability to dynamically control protein-protein interactions and localization of proteins is critical in synthetic biological systems. Here the authors develop a peptide-based molecular switch that regulates dimer formation and lipid membrane targeting via reversible phosphorylation.

Functional catalytic triads have been designed into a hyperstable heptameric α-helical barrel protein. Twenty-one mutations were introduced to form seven Cys-His-Glu catalytic triads. The resulting protein hydrolyses p-nitrophenyl acetate with activities matching the most-efficient redesigned hydrolases based on natural protein scaffolds. This is the first example of a functional catalytic triad being engineered into a fully de novo protein.

Proteins rely on a combination of intramolecular forces to form and stabilize their structures. A careful comparison of computational analysis and high-resolution crystal structures now indicates that the n→π* interaction merits inclusion in this group.

The design and mutagenesis of an α-helix-containing monomeric miniprotein, PPα-Tyr, provide insights into weak noncovalent CH–π interactions that help define and stabilize folded proteins and protein–ligand interactions.

So far most of the de novo designed proteins are for single states only. Here, the authors present the de novo design and crystal structure determination of a coiled-coil peptide that assembles into multiple, distinct conformational states under the same conditions and further characterise its properties with biophysical experiments, NMR and MD simulations.

The de novo design of functional membrane proteins is a formidable challenge. Now, water-soluble peptides have been designed that assemble into α-helical barrels with accessible, polar and hydrated central channels. Insights from these structures have been used to produce stable membrane-spanning, cation-selective channels.

The assembly of transmembrane barrels formed from short synthetic peptides has not been previously demonstrated. Now, a transmembrane pore has been fabricated via the self-assembly of peptides. The 35-amino-acid α-helical peptides are based on the C-terminal D4 domain of the Escherichia coli polysaccharide transporter Wza.

Two complementary coiled-coil peptides and a bacterial microcompartment shell protein are combined to construct cytoscaffolds within Escherichia coli cells. Targeting enzymes to the cytoplasmic scaffold results in colocalization and improved metabolic flux.

Supramolecular ordered networks are formed through directional interactions of uniform macromonomer building blocks. Now it has been shown that, rather than intermolecular affinity, the flexibility of the binding interface (‘interface flexibility’) dominates the mechanism of self-assembly. This study provides an intuitive understanding of the role of interface flexibility in supramolecular self-assembly.

Hydrogels are hydrated polymer networks with applications in biotechnology and medicine. When created from alpha-helical peptides with engineered peptide sequences, their formation mechanisms can be controlled, leading to diverse properties. For instance, those with hydrogen-bonded networks melt on heating, but those formed through hydrophobic interactions strengthen when warmed.

Bacterial microcompartments (BMCs) are protein-bound organelles encapsulating segments of metabolic pathways. Here the authors utilize specific de novo coiled-coil protein-protein interactions to display proteins on the outer or inner surface of BMCs.

Computational protein design uses information on the constraints of the biological and physical properties of proteins for protein engineering and de novo protein design. In this Primer, Albanese et al. give an overview of the guiding principles of computational protein design and its considerations, methods and applications and conclude by discussing the future of the technique in the context of rapidly advancing computational tools.

A new 20-residue peptide represents the smallest example to date of cooperatively folded tertiary structure. This achievement provides a new tool for elucidating protein conformational preferences. The mini-protein should serve as a fruitful platform for protein design.

Thomas et al. test 6 ELISAs detecting IgA and IgG antibodies to whole SARS-CoV-2 spike protein, to its receptor binding domain region and to nucleocapsid protein in saliva. Across 20 household outbreaks, antibody responses are heterogeneous, but a reliable indicator of recent infection.