3e07
Crystal structure of spatzle cystine knot
Structural highlights
FunctionSPZ_DROME Component of the extracellular signaling pathway that establishes the dorsal-ventral pathway of the embryo. Three proteases; ndl, gd and snk process easter to create active easter. Active easter defines cell identities along the dorsal-ventral continuum by activating the spz ligand for the Tl receptor in the ventral region of the embryo. Spz C-106 in the hemolymph controls expression of the antifungal peptide Drosomycin (Drs) by acting as a ligand of Tl and inducing an intracellular signaling pathway.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe Drosophila Spatzle protein, involved in the embryonic development of the dorsal-ventral axis and in the adult immune response, is expressed as a proprotein and is activated by the serine proteinases Easter or Spatzle-processing enzyme. Proteolytic cleavage generates a 106-amino acid COOH-terminal fragment, C106, homologous to the mature form of nerve growth factor NGF, a cystine knot protein. Through alternative splicing, the Spatzle gene encodes for several isoforms that (with one exception, the "propeptide isoform") share C106 but differ in the prosequence. Three isoforms have been expressed recombinantly in Escherichia coli strains. The propeptide isoform could be expressed in soluble form and is unstructured according to CD and NMR measurements. Dimeric full-length Spatzle isoforms have been refolded from insoluble inclusion bodies and are able to rescue Spatzle-deficient embryos. Although the two full-length isoforms exhibit similar far-UV CD spectra, large differences in tryptophan fluorescence quenching by the respective pro-parts are observed. Both full-length isoforms exhibited highly cooperative folding transitions. Proteolytic digestion using trypsin resulted in C106, whose unfolding exhibits lower thermodynamic stability and cooperativity compared with the full-length proteins. The structure of C106 reveals a T-shaped dimer with significant differences to NGF and a deep internal cavity. Substantial beta-sheet formation is observed between the two monomers, whereas a long loop containing the single tryptophan residue is disordered in the crystals. Our results suggest that the propeptides stabilize the tertiary structure of the "mature" Spatzle cystine knot. Biophysical characterization of refolded Drosophila Spatzle, a cystine knot protein, reveals distinct properties of three isoforms.,Hoffmann A, Funkner A, Neumann P, Juhnke S, Walther M, Schierhorn A, Weininger U, Balbach J, Reuter G, Stubbs MT J Biol Chem. 2008 Nov 21;283(47):32598-609. Epub 2008 Sep 12. PMID:18790733[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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