Nanobody-aided structure determination of the EpsI:EpsJ pseudopilin heterodimer from Vibrio vulnificus.

Pseudopilins form the central pseudopilus of the sophisticated bacterial type 2 secretion systems. The crystallization of the EpsI:EpsJ pseudopilin heterodimer from Vibrio vulnificus was greatly accelerated by the use of nanobodies, which are the smallest antigen-binding fragments derived from heavy-chain only camelid antibodies. Seven anti-EpsI:EpsJ nanobodies were generated and co-crystallization of EpsI:EpsJ nanobody complexes yielded several crystal forms very rapidly.