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© 2020 American Chemical Society. The self-assembly of collagen-mimetic peptides (CMPs) that form sticky-ended triple helices has allowed the production of surprisingly stable artificial collagen fibers and hydrogels. Assembly through sticky ends requires the recognition of a single strand by a templated strand dimer. Although CMPs and their triple helices have been studied extensively, the structure of a strand dimer is unknown. Here, we evaluate the physical characteristics of such dimers, using disulfide-templated (PPG)10 dimers as a model. Such "linked-dimers" retain their collagen-like structure even in the absence of a third strand, but only when their strands are capable of adopting a triple-helical fold. The intrinsic collagen-like structure of templated CMP pairs helps to explain the success of sticky-ended CMP association and changes the conception of new synthetic collagen designs.

Collagen is an abundant component of the extracellular matrix and connective tissues. Some collagen-mimetic peptides (CMPs) that do not form homotrimers can anneal to damaged tissue. Here, through acomputational screen, we identify (flpHypGly)₇as an optimal monomeric CMP for heterotrimer formation.Wefind that (flpHypGly)₇ forms stable triple helices with (ProProGly)₇ but not with itself. The nonnaturalamino acid HflpOH, which is (2S,4S)-4-fluoroproline, is not toxic to humanfibroblasts or keratinocytes.Conjugation of (flpHypGly)₇ to afluorescent dye enables the facile detection of burned collagenoustissue with high specificity. The ubiquity of collagen and the prevalence of injuries and diseases thatdisrupt endogenous collagen suggests widespread utility for this approach., National Institutes of Health (U.S.) (Grant R56 AR044276)

Collagen is the most abundant protein in humans and the major component of human skin. Collagen mimetic peptides (CMPs) can anneal to damaged collagen in vitro and in vivo. A duplex of CMPs was envisioned as a macromolecular mimic for damaged collagen. The duplex was synthesized on a solid support from the amino groups of a lysine residue and by using olefin metathesis to link the N termini. The resulting cyclic peptide, which is a monomer in solution, binds to CMPs to form a triple helix. Among these, CMPs that are engineered to avoid the formation of homotrimers but preorganized to adopt the conformation of a collagen strand exhibit enhanced association. Thus, this cyclic peptide enables the assessment of CMPs for utility in annealing to damaged collagen. Such CMPs have potential use in the diagnosis and treatment of fibrotic diseases and wounds., NIH (Grant R56 AR044276)

Pancreatic-type ribonucleases (ptRNases) are prevalent secretory enzymes that catalyze the cleavage of RNA. Ribonuclease inhibitor (RI) is a cytosolic protein that has femtomolar affinity for ptRNases, affording protection from the toxic catalytic activity of ptRNases, which can invade human cells. A human ptRNase variant that is resistant to inhibition by RI is a cytotoxin that is undergoing a clinical trial as a cancer chemotherapeutic agent. We find that the ptRNase and protein kinases in the ERK pathway exhibit strongly synergistic toxicity toward lung cancer cells (including a KRAS[superscript G12C] variant) and melanoma cells (including BRAF[superscript V600E] variants). The synergism arises from inhibiting the phosphorylation of RI and thereby diminishing its affinity for the ptRNase. These findings link seemingly unrelated cellular processes, and suggest that the use of a kinase inhibitor to unleash a cytotoxic enzyme could lead to beneficial manifestations in the clinic., National Institutes of Health (U.S.) (Grant R01 CA073808)