Crystallization and preliminary X-ray crystallographic studies of succinic semialdehyde dehydrogenase from Streptococcus pyogenes

Succinic semialdehyde dehydrogenase (SSADH) plays a critical role in the metabolism of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) and catalyzes the NAD(P) ⁺-coupled oxidation of succinic semialdehyde (SSA) to succinic acid (SA). SSADH from Streptococcus pyogenes has been purified and crystallized as the apoenzyme and in a complex with NAD ⁺. The crystals of native and NAD ⁺-complexed SSADH diffracted to resolutions of 1.6 and 1.7 Å, respectively, using a synchrotron-radiation source. Both crystals belonged to the orthorhombic space group P2 ₁2 ₁2 ₁, with unit-cell parameters a = 93.3, b = 100.3, c = 105.1 Å for the native crystal and a = 93.3, b = 100.3, c = 105.0 Å for the complex crystal. Preliminary molecular replacement confirmed the presence of one dimer in both crystals, corresponding to a Matthews coefficient (V _M) of 2.37 Å ³ Da ^-1 and a solvent content of 48.0%.