Jerdostatin represents a novel RTS-containing short disintegrin cloned by RT-PCR from the venom gland mRNA of the chinese Jerdon´s pit viper Trimeresurus jerdonii. The jerdostatin´s precursor cDNA contained a 333 bp ORF encoding a signal peptide, a pre-peptide and a 43-amino-acid disintegrin domain, whose amino acid sequence displayed 80% identity with that of the KTS-disintegrins obtustatin and viperistatin. The jerdostatin cDNA structure represents the first complete ORF of a short disintegrin and points to the emergence of jerdostatin from a short-coding gene. The different residues between jerdostatin and obtustatin/viperistatin are segregated within the integrin-recognition loop and the C-terminal tail. Native jerdostatin (r-jerdostatin-R21) and a R21/K mutant (r-jerdostatin-K21) were produced in E. coli. In each case, two conformers were isolated. 1D 1H NMR showed that conformers 1 and 2 of r-jerdostatin-R21 represent, respectively, well-folded and unfolded proteins. The two conformers of the wild-type and the R21/K mutant inhibited the adhesion of 1K562 cells to collagen IV with IC50s of 180 nM and 703 nM, respectively. The IC50s of the conformers 2 of r-jerdostatin-R21 and r-jerdostatin-K21 were, respectively, 5.95 M and 12.5 M. Neither r-jerdostatin-R21 nor r-jerdostatin-K21 showed inhibitory activity towards other integrins, including IIb3, v3, 21, 41, 51, 61, and 91 up to a concentration of 24 M. Although the RTS motif appears to be more potent than KTS inhibiting the 11 integrin, r-jerdostatin-R21 is less active than the KTS-disintegrins strongly suggesting that substitutions outside the integrin-binding motif and/or C-terminal proteolytic processing are responsible for the decreased inhibitory activity.