The crystal structures of two spermadhesins reveal the CUB domain fold.

Spermadhesins, 12,000–14,000 Mr mammalian proteins, include lectins involved in sperm–egg binding and display a single CUB domain architecture. We report the crystal structures of porcine seminal plasma PSP-I/PSP-II, a heterodimer of two glycosylated spermadhesins, and bovine aSFP at 2.4 A and 1.9 A resolution respectively.