To obtain an RRF protein crystal useful for elucidating a stereostructure of ribosome recycling factor(RRF), developing various antimicrobial agents, herbicides, or the like, because of an RRF of orthorhombic system.

This RRF protein crystal is crystallized by a hanging drop vapor diffusion technique method, is of orthorhombic system, has a space group P21212 and a 30×50×250 μm size. RRF is derived from a microorganism X and the crystal is any of crystal of RRF protein itself, crystal of RRF variant, crystal of RRF protein homolog, crystal of RRF protein variant, crystal of RRF protein homolog and crystal of RRF protein cocomplex. In designing a compound to be bonded to the active site of the RRF protein, in order to evaluate its chemical experimental body, preferably structural information obtained from the crystal of the RRF protein is used.