Synthetic antibodies for specific recognition and crystallization of structured RNA

Ye JD, Tereshko V, Frederiksen JK, Koide A, Fellouse FA, Sidhu SS, Koide S, Kossiakoff AA, Piccirilli JA

Proc. Natl. Acad. Sci. U.S.A. 2008 Jan;105(1):82-7

PMID: 18162543


Antibodies that bind protein antigens are indispensable in biochemical research and modern medicine. However, knowledge of RNA-binding antibodies and their application in the ever-growing RNA field is lacking. Here we have developed a robust approach using a synthetic phage-display library to select specific antigen-binding fragments (Fabs) targeting a large functional RNA. We have solved the crystal structure of the first Fab-RNA complex at 1.95 A. Capability in phasing and crystal contact formation suggests that the Fab provides a potentially valuable crystal chaperone for RNA. The crystal structure reveals that the Fab achieves specific RNA binding on a shallow surface with complementarity-determining region (CDR) sequence diversity, length variability, and main-chain conformational plasticity. The Fab-RNA interface also differs significantly from Fab-protein interfaces in amino acid composition and light-chain participation. These findings yield valuable insights for engineering of Fabs as RNA-binding modules and facilitate further development of Fabs as possible therapeutic drugs and biochemical tools to explore RNA biology.