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Genetically grafting macrocyclic peptides into the structural loops of fragment crystallizable regions can make them surrogate receptor agonists with longer half-lives in circulation and enhanced penetration of the blood–brain barrier.

Genetic code reprogramming enables ribosomal incorporation of nonproteinogenic amino acids for peptide development. The authors introduce a flexizyme system using phenol esters, improving aminoacylation efficiency and expanding ribosomal synthesis of diverse nonstandard peptides.

A single-cell multiomic immune cell atlas from 235 Japanese, including patients with COVID-19 and healthy individuals, linked with host genetics including germline and somatic mutation, plasma proteomics and metagenomics data reveals that immune cells are dynamically regulated in a cell state-dependent manner.

A potent inhibitor for hepatocyte growth factor was identified that utilizes an allosteric mode of inhibition revealed by atomic force microscopy imaging. The inhibitor could be used for positron emission tomography imaging of mouse tumors.

Flexizymes can be used to prepare nonproteinogenic aminoacyl-tRNAs (npAA-tRNAs) by activating amino acids with suitable leaving groups, leading to ribosomal incorporation of npAAs by genetic code reprogramming. This enables the ribosomal synthesis of unique peptides and proteins containing various npAAs.

Walport & coworkers report cell-active, potent and selective cyclic peptide modulators for the enzyme peptidylarginine deiminase PADI4/PAD4, including an inhibitor, an activator and an affinity molecule, revealing insights into PADI4 regulation.

Flexizyme is an in vitro evolved ribozyme which can specifically add an amino acid onto the terminal 3'OH of a tRNA. The structure of flexizyme joined to a tRNA mimic is solved. Interestingly, the RNA displays many of the known aminoacyl tRNA synthetase–tRNA interactions, approaches the tRNA in a similar manner, and exhibits an induced fit conformation that enhances specificity.

In vitro screening of a ribosomally synthesized macrocyclic peptide library containing cyclic γ^2,4-amino acids (cγAA) afforded the discovery of potent inhibitors of the SARS-CoV-2 main protease (M^pro). A co-crystal structure revealed the contribution of this cγAA to M^pro binding and the proteolytic stability of these macrocycles.

Despite recent advances in engineering of in vitro translation systems, direct ribosomal incorporation of hydroxyhydrocarbon moieties—which can endow peptides with unique biochemical/folding properties—remains challenging. Now, incorporation of translation-compatible azide/hydroxy acids and their post-translational tandem backbone-acyl shifts have enabled in vitro ribosomal synthesis of peptides containing various hydroxyhydrocarbon units.

His-C2-directed modification is chemically challenging and rarely occurs in nature due to the low reactivity of this position. Now, the prenlytransferase LimF has been discovered and applied for geranylation of histidine-containing peptides and imidazole-containing small molecules, showcasing the versatility of this biocatalyst.

Finding a selective modulator of Lys63-linked ubiquitin chains has proven very challenging. Here, the authors develop potent macrocyclic peptide binders of Lys63-linked di-ubiquitin chains that interrupt DNA damage repair and lead to apoptotic cell death.

RaPID (Random non-standard Peptides Integrated Discovery) enables discovery of small macrocyclic peptides binding desired targets. Here, the authors propose lasso-grafting: the RaPID-derived peptides are implanted onto diverse proteins and maintain both the binding properties of the cyclic peptide and the host protein function.

Azoles are five-membered heterocycles found in peptidic natural products and synthetic peptiodomimetics. Here the authors demonstrate a posttranslational chemical modification method for in vitro ribosomal synthesis of peptides with exotic azole groups at specific positions.

Macrocyclic peptides were recently discovered as potent modulators of ubiquitin-mediated cellular signaling pathways. Here the authors used multidisciplinary approach to uncover how macrocyclic peptides that inhibit proteasomal degradation selectively recognize long Lys48-linked polyubiquitin chains.

Lactazole A is a thiopeptide from Streptomyces lactacystinaeus, encoded by a compact 9.8 kb biosynthetic gene cluster. Here, the authors show a platform for in vitro biosynthesis of lactazole A via a combination of a flexible in vitro translation system with recombinantly produced lactazole biosynthetic enzymes.

River blindness, a disease affecting millions throughout the tropics, is caused by parasitic worms. Here, Yuet al. report the discovery and structural characterization of potent macrocyclic peptide inhibitors of iPGM, a nematode-specific phosphoglycerate mutase, as potential leads for novel antimicrobial agents.

JmjC histone demethylases (KDMs) are cancer targets due to their links to cell proliferation, but selective inhibition remains a challenge. Here the authors identify potent inhibitors of KDM4A-C—viain vitroselection from a vast library of cyclic peptides—that show selectivity over other KDMs.

The development of small volume chamber arrays has greatly facilitated high throughput biological assays of soluble proteins. Here, Watanabe et al.adapt this approach to develop an arrayed lipid bilayer chamber system for single molecule level measurements of membrane transporter activity.

Activation of the Met receptor by hepatocyte growth factor requires Met receptor dimerization. Here, the authors identify Met-binding peptide macrocycles that, in a dimeric form as a result of chemical crosslinking, induce Met receptor dimerization and activation in cultured human cells.

Here, the authors report bi-functional, wide tropic macrocycles that bind the influenza viral envelope protein hemagglutinin and inhibit virus infection by blocking adsorption and fusion and show efficacy in preventing severe pneumonia at later stages of infection in mouse and non-human primate cynomolgus macaque models.

Modulating particular ubiquitin chains using binding molecules is challenging given the diversity of chain lengths and linkages found in vivo. Now, tight binding modulators that are specific to K48-linked ubiquitin chains have been found by combining protein synthesis and screening of macrocyclic peptide ligands.

The authors develop a ribozyme, Tx2.1, that is capable of aminoacylating tRNA with specificity for the anticodon from directed evolution of a T-box riboswitch. Tx2.1 could be used to charge non-natural amino acids in an in vitro translation system.

Peripheral blood mononuclear cells from 73 Japanese patients with coronavirus disease 2019 (COVID-19) and 75 healthy controls were analyzed using single-cell transcriptomics. Combining these data with genotyping data highlights the interplay between host genetics and the immune response in modulating disease severity.

The repertoire of amino acids available for ribosomal peptide synthesis is limited by the genetic code. Now, a method to reduce the redundancy of codons has been developed based on the artificial division of codon boxes. This method enables non-proteinogenic amino acids to be included in peptides without sacrificing proteinogenic ones.

Goadsporin is an antibacterial peptide highly customized by multiple post-translational modifying enzymes. Here, the authors dissect its biosynthetic pathway byin vitro reconstitution and use their insights to produce goadsporin analogues in vitro and in vivo.

The conserved A32-U38 pair in the anticodon loop of tRNA^Ala_GGC is now shown to be important for accurate decoding. Using tRNA^Ala variants in this pair in an in vitro translation system showed that some variants could decode both the cognate and a near-cognate codons with high efficiency. These mutants tRNA were toxic in vivo, supporting the biological relevance of this accuracy determinant.

The extent to which peptide synthesis by the ribosome can tolerate the inclusion of non-peptidic components is not clear. Yet such hybrids would expand the range of ribosomally synthesized structures. Now it has been shown that tRNAs acylated by aromatic foldamers can initiate the ribosomal synthesis of non-cyclic and cyclic foldamer–peptide hybrid molecules. The oligo-aryl segments contain folding information that can control peptide conformation in the hybrids.

Ribosomes tend to stall during the translation of consecutive proline residues, which can be rescued by the co-translational factor EF-P. Here the authors identify a structural element of tRNA^Proresponsible for specific recognition by EF-P and stimulation of Pro-Pro peptide bond formation.

Macrophages have a role in the pathogenesis of pulmonary emphysema. Here the authors show that inhalation—but not oral delivery—of the anti-osteoporosis drug alendronate attenuates lung damage in a mouse model of emphysema by inducing apoptosis of alveolar macrophages.

Cyclic β-amino acids can add useful properties to peptides, such as inducing turn structures or providing resistance to proteases. To harness these properties up to ten consecutive cyclic β-amino acids have now been ribosomally incorporated via genetic code reprogramming into a foldamer peptide library that has been screened for potent binders against a protein target, human factor XIIa.

Several X-ray crystal structures of an H⁺-driven multidrug and toxic compound extrusion (MATE) transporter from Pyrococcus furiosus are presented, whose complex structure with macrocyclic peptides may help facilitate the discovery of efficient inhibitors of MATE transporters.

Genetic code reprogramming has generally focused on changing the translation step of protein expression, altering what each codon specifies. Mutations in the peptidyl transferase center, along with compensatory mutations in the C-termini of tRNAs, now provide an alternate method to create fully orthogonal ribosomes.