The serine acetyltransferase from Escherichia coli

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Abstract
An expression vector has been constructed which increases the expression of serine acetyltransferase (SAT) from E. coli to 17% of the soluble cell protein. A novel purification procedure, using dye‐affinity chromatography, allows purification of SAT to homogeneity. The enzyme has been crystallised from polyethylene glycol, in the presence of L‐cysteine (an inhibitor of SAT). The crystals which diffract to beyond 3.0 Å resolution are of the tetragonal spacegroup P41212(or P43212) with cell dimensions a = b = 123 Å, c = 79 Å. Since ultracentrifugation and gel‐filtration experiments indicate that purified SAT is a tetramer, there appears to be one‐half tetramer in the asymmetric unit (V m = 2.55 Å3/Da).