The molecular structure of human uropepsin, an aspartic proteinase from the
urine produced in the form of pepsinogen A in the gastric mucosa, has been
determined by molecular replacement using human pepsin as the search model
. Crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a
= 50.99, b = 75.56, c = 89.90 Angstrom. Crystallographic refinement led to
an R factor of 0.161 at 2.45 Angstrom resolution. The positions of 2437 no
n-H protein atoms in 326 residues have been determined and the model contai
ns 143 water molecules. The structure is bilobal, consisting of two predomi
nantly beta -sheet lobes which, as observed in other aspartic proteinases,
are related by a pseudo-twofold axis. A model of the uropepsin-pepstatin co
mplex has been constructed based on the high-resolution crystal structure o
f pepsin complexed with pepstatin.