CRYSTAL-STRUCTURE OF POKEWEED ANTIVIRAL PROTEIN FROM SEEDS OF PHYTOLACCA-AMERICANA AT 0.25 NM

Crystals of pokeweed antiviral protein (PAP) from seeds of Phytolacca americana with high diffraction ability were grown from high protein c oncentration (100 mg/mL) solution at high temperature (33 degrees C). The crystal structure was solved by use of molecular replacement metho d and refined by use of molecular dynamic method at 0.25 nm to an R fa ctor of 18.15% with standard deviations from standard geometry of 0.00 1 6 nm and 2.04 degrees for bond lengths and bond angles, respectively . Comparison with two other PAPs revealed, near the active center, a s equence and structure-variable region, consisting of the loop connecti ng the fifth beta-strand with the second a-helix and including a propo sed active residue, suggesting this loop probably to be related to dif ference in activity.