Crystallization and preliminary X-ray analysis of peanut agglutinin-N6-benzylaminopurine complex.

Preliminary diffraction data collected on peanut agglutinin (PNA) crystals grown in the presence of N6-benzylaminopurine (BAP) indicate a monoclinic cell (P2) with a = 67.0 A, b = 35.2 A, c = 65.8 A and beta = 68.6 degrees. This is the first example of a legume lectin crystallized with a bound phytohormone. Crystals of PNA grown previously in the presence of lactose had an orthorhombic space group (P2(1)2(1)2) with a = 128.8 A, b = 126.0 A and c = 76.1 A and one tetramer per asymmetric unit. The Vm value for the PNA-BAP crystals is 2.62 A3/Da, assuming one monomer of PNA per asymmetric unit. Thus, while the PNA-lactose complex crystallized as tetramers, the PNA-BAP complex has, at most, dimers in the crystal. These results indicate that BAP, a naturally occurring phytohormone, can modify the quaternary structure of PNA by dissociation and change its carbohydrate valence.