Subramanian E, Liu M, Swan I D, Davies D R
Adv Exp Med Biol. 1977;95:33-41. doi: 10.1007/978-1-4757-0719-9_3.
This paper contains a preliminary report of the crystal structure of the acid protease from Rhizopus chinensis at 2.5 A resolution. The molecule is bilobal with a large cleft between the lobes. Pepstatin binds in the cleft near the catalytically active Asp-35. The overall folding of the molecule consists primarily of antiparallel beta-strands, there being only four small helices.