The only crystal structure of full-length Dicer to date is that of G. intestinalis protein (Gi-Dicer), which consists of two endoNDs, PAZ and platform domains. The structure of Gi-Dicer has been likened to a hatchet with the dimeric endoNDs forming the blade and the PAZ at the end of the handle. Gi-Dicer cleaves dsRNA to 25 bps with 2 nt overhang at the 3? end. Using structures of bacterial RNase III-dsRNA and PAZ-nucleic acid complexes as templates, a model of Gi-Dicer - dsRNA complex was proposed. The platform domain between the endoND and PAZ appears to have a positively charged flat surface for dsRNA binding and separates the cleavage site (endoND) from the 3? end (PAZ) by ~25-bps.
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