Accelerated Publication - Chitin-binding proteins in invertebrates and plants comprise a common chitin-binding structural motif

Tachycitin, a 73-residue polypeptide having antimicrobial activity is prese nt in the hemocyte of horseshoe crab (Tachypleus tridentatus). The first th ree-dimensional structure of invertebrate chitin-binding protein was determ ined for tachycitin using two-dimensional nuclear magnetic resonance spectr oscopy. The measurements indicate that the structure of tachycitin is large ly divided into N- and C-terminal domains; the former comprises a three-str anded beta-sheet and the latter a two-stranded beta-sheet following a short helical turn. The latter structural. motif shares a significant tertiary s tructural similarity with the chitin-binding domain of plant chitin-binding protein. This result is thought to provide faithful experimental evidence to the recent hypothesis that chitin-binding proteins of invertebrates and plants are correlated by a convergent evolution process.