The crystallization of amidase, the ultimate enzyme in the Trp-dependent auxin-biosynthesis pathway, fromArabidopsis thalianawas attempted using protein samples with at least 95% purity. Cube-shaped crystals that were assumed to be amidase crystals that belonged to space groupI4 (unit-cell parametersa=b= 128.6,c= 249.7 Å) were obtained and diffracted to 3.0 Å resolution. Molecular replacement using structures from the PDB containing the amidase signature fold as search models was unsuccessful in yielding a convincing solution. Using theSequence-Independent Molecular replacement Based on Available Databases(SIMBAD) program, it was discovered that the structure corresponded to dihydrolipoamide succinyltransferase fromEscherichia coli(PDB entry 1c4t), which is considered to be a common crystallization contaminant protein. The structure was refined to anR_workof 23.0% and anR_freeof 27.2% at 3.0 Å resolution. The structure was compared with others of the same protein deposited in the PDB. This is the first report of the structure of dihydrolipoamide succinyltransferase isolated without an expression tag and in this novel crystal form.