Progress Toward the Tertiary Structure of (Class 3) Aldehyde Dehydrogenase

Abstract

We chose to pursue crystallography of the class 3 aldehyde dehydrogenase since, with subunits some 10% shorter than classes 1 and 2, and a dimeric rather than tetrameric quaternary structure, it presented a simpler molecule to solve. Further, despite a primary structure only some 30% identical to class 1 or 2 structures, secondary structural predictions suggested generally comparable tertiary structures (Hempel et al., 1989). The pTALDH expression system (Harper et al., 1988) provided a ready source of material. Subsequently, the observed low solubility of the enzyme (ca. lmg/ml in the presence of NAD) was probably a further advantage aiding crystallization.