A structural motif, the tryptophan zipper (trpzip), greatly stabilizes the β-hairpin conformation in short peptides. Peptides (12 or 16 aa in length) with four different turn sequences are monomeric and fold cooperatively in water, as has been observed previously for some hairpin peptides. However, the folding free energies of the trpzips exceed substantially those of all previously reported β-hairpins and even those of some larger designed proteins. NMR structures of three of the trpzip peptides reveal exceptionally well-defined β-hairpin conformations stabilized by cross-strand pairs of indole rings. The trpzips are the smallest peptides to adopt an unique tertiary fold without requiring metal binding, unusual amino acids, or disulfide crosslinks.

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The Ras gene is frequently mutated in cancer, and mutant Ras drives tumorigenesis. Although Ras is a central oncogene, small molecules that bind to Ras in a well-defined manner and exert inhibitory effects have not been uncovered to date. Through an NMR-based fragment screen, we identified a group of small molecules that all bind to a common site on Ras. High-resolution cocrystal structures delineated a unique ligand-binding pocket on the Ras protein that is adjacent to the switch I/II regions and can be expanded upon compound binding. Structure analysis predicts that compound-binding interferes with the Ras/SOS interactions. Indeed, selected compounds inhibit SOS-mediated nucleotide exchange and prevent Ras activation by blocking the formation of intermediates of the exchange reaction. The discovery of a small-molecule binding pocket on Ras with functional significance provides a new direction in the search of therapeutically effective inhibitors of the Ras oncoprotein.small G protein | guanine nucleotide exchange | nuclear magnetic resonance | crystal structure | small-molecule inhibitors R as is a small GTP-binding protein that functions as a nucleotide-dependent switch for central growth signaling pathways (1, 2). In response to extracellular signals, Ras is converted from a GDP-bound (Ras GDP ) to a GTP-bound (Ras GTP ) state, as catalyzed by guanine nucleotide exchange factors (GEFs), notably the SOS1 protein. Active Ras GTP mediates its diverse growth-stimulating functions through its direct interactions with effectors including Raf, PI3K, and Ral guanine nucleotide dissociation stimulator. The intrinsic GTPase activity of Ras then hydrolyzes GTP to GDP to terminate Ras signaling. The Ras GTPase activity can be further accelerated by its interactions with GTPase-activating proteins (GAPs), including the neurofibromin 1 tumor suppressor (2).Ras, a human oncogene identified and characterized over 30 y ago, is mutated in more than 20% of human cancers. Among the three Ras isoforms (K, N, and H), KRas is most frequently mutated (2). Mutant Ras has a reduced GTPase activity, which prolongs its activated conformation, thereby promoting Rasdependent signaling and cancer cell survival or growth (1, 2).Mutations of Ras in cancer are associated with poor prognosis (2). Inactivation of oncogenic Ras in mice results in tumor shrinkage. Thus, Ras is widely considered an oncology target of exceptional importance. However, development of small-molecule inhibitors against Ras has thus far proven unsuccessful. Given the picomolar affinity between guanine nucleotides and Ras and the high cytosolic concentration of guanine nucleotides, it is very challenging to develop a conventional inhibitor competitive against nucleotide binding (1, 2). Outside of the nucleotide-binding pocket, the Ras protein does not contain obvious cavities for small-molecule binding. A number of small molecules have been reported to bind to Ras (3-7), but their mechanisms of action and the structural basis to achieve Ras inhibition remain elusive.Fra...

Bronchoalveolar lavage fluid from mice with experimentally induced allergic pulmonary inflammation contains a novel 9.4 kDa cysteine‐rich secreted protein, FIZZ1 (found in inflammatory zone). Murine (m) FIZZ1 is the founding member of a new gene family including two other murine genes expressed, respectively, in intestinal crypt epithelium and white adipose tissue, and two related human genes. In control mice, FIZZ1 mRNA and protein expression occur at low levels in a subset of bronchial epithelial cells and in non‐neuronal cells adjacent to neurovascular bundles in the peribronchial stroma, and in the wall of the large and small bowel. During allergic pulmonary inflammation, mFIZZ1 expression markedly increases in hypertrophic, hyperplastic bronchial epithelium and appears in type II alveolar pneumocytes. In vitro, recombinant mFIZZ1 inhibits the nerve growth factor (NGF)‐mediated survival of rat embryonic day 14 dorsal root ganglion (DRG) neurons and NGF‐induced CGRP gene expression in adult rat DRG neurons. In vivo, FIZZ1 may modulate the function of neurons innervating the bronchial tree, thereby altering the local tissue response to allergic pulmonary inflammation.

The results offer the first details at an atomic level of the interaction between a chemokine and its receptor. Consideration of other biochemical data allow extrapolation to a model for the interaction of IL-8 with the full-length receptor. In this model, the heparin-binding residues of IL-8 are exposed, thereby allowing presentation of the chemokine from endothelial cell-surface glycosaminoglycans. This first glimpse of how IL-8 binds to its receptor provides a foundation for the structure-based design of chemokine antagonists.