English: The RNA silencing suppressor p19 from the tomato bushy stunt virus, rendered from PDB ID 1R9F. The protein forms a dimer whose two monomers are shown in blue and green. The dimer forms an interaction surface that binds double-stranded RNAs of 19 to 21 base pairs. Plants use RNA silencing as a defense mechanism against viruses; the p19 protein serves as a viral counter-defense that specifically binds siRNAs and suppresses the silencing machinery.

Keqiong Ye, Lucy Malinina & Dinshaw J. Patel. Recognition of small interfering RNA by a viral suppressor of RNA silencing. Nature 426, 874-878 (18 December 2003). DOI: 10.1038/nature02213.

http://www.nature.com/nature/journal/v426/n6968/full/nature02213.html