Crystal structures of the Chromobacteriumviolaceum omega -transaminase reveal major structural rearrangements upon binding of coenzyme PLP

The bacterial omega -transaminase from Chromobacteriumviolaceum (Cv- omega TA, ) catalyses industrially important transamination reactions by use of the coenzyme pyridoxal 5'-phosphate (PLP). Here, we present four crystal structures of Cv- omega TA: two in the apo form, one in the holo form and one in an intermediate state, at resolutions between 1.35 and 2.4Aa. The enzyme is a homodimer with a molecular mass of similar to 100kDa. Each monomer has an active site at the dimeric interface that involves amino acid residues from both subunits. The apo-Cv- omega TA structure reveals unique 'relaxed' conformations of three critical loops involved in structuring the active site that have not previously been seen in a transaminase. Analysis of the four crystal structures reveals major structural rearrangements involving elements of the large and small domains of both monomers that reorganize the active site in the presence of PLP. The conformational change appears to be triggered by binding of the phosphate group of PLP. Furthermore, one of the apo structures shows a disordered 'roof' over the PLP-binding site, whereas in the other apo form and the holo form the 'roof' is ordered. Comparison with other known transaminase crystal structures suggests that ordering of the 'roof' structure may be associated with substrate binding in Cv- omega TA and some other transaminases. The atomic coordinates and structure factors for the Chromobacteriumviolaceum omega -transaminase crystal structures can be found in the RCSB Protein Data Bank () under the accession codes for the holoenzyme, for the apo1 form, for the apo2 form and for the mixed form times and by () We present four crystal structures of the industrially important omega -transaminase from Chromobacteriumviolaceum in apo, PLP-containing and intermediate forms. The apo structure reveals unique 'relaxed' conformations of critical loops involved in structuring the active site. Analysis of the four crystal structures reveals major structural rearrangements involving elements of both monomers that reorganize the active site in the presence of PLP.