Crystal structure of Glutamate1-semialdehyde aminotransferase from Bacillus subtilis with bound pyridoxamine-5′-phosphate

► GSA-ATBsu exits as the double PMP form in solution without the exotic cofactor addition after purification. ► GSA-ATBsu structure shows the symmetry at the open gating loop region as well as identical cofactor (PMP) binding in each monomer. ► GSA-ATBsu structure supports one reaction mechanism suggested for this enzyme. ► The symmetry of GSA-ATBsu structure challenges the previously proposed negative cooperativity between monomers of this enzyme.