Symmetry, molecular weight and crystallographic data for sweet potato β-amylase

Abstract

Sweet potato β-amylase has been crystallized in the tetragonal space group P4 122 (or enantiomorph) with unit cell dimensions a = b = 210.7 A ̊ , c = 157.0 A ̊ . A new method has been developed by which accurate molecular weight values can be obtained from protein crystals grown from concentrated salt solutions. The method also gives the hydration of the protein in the crystal. Using this new technique the molecular weight of β-amylase was found to be 206,000 ± 10,000. The enzyme is tetrameric with molecular symmetry which includes, at least to low resolution, a diad axis