3-DIMENSIONAL STRUCTURE IN SOLUTION OF THE N-TERMINAL LIPOYL DOMAIN OF THE PYRUVATE-DEHYDROGENASE COMPLEX FROM AZOTOBACTER-VINELANDII

The three-dimensional structure of the N-terminal lipoyl domain of the acetyltransferase component of the pyruvate dehydrogenase complex fro m Azotobacter vinelandii has been determined using heteronuclear multi dimensional NMR spectroscopy and dynamical simulated annealing. The st ructure is compared with the solution structure of the lipoyl domain o f the A. vinelandii 2-oxoglutarate dehydrogenase complex. The overall fold of the two structures, described as a beta-barrel-sandwich hybrid , is very similar. This agrees well with the high similarity of NMR-de rived parameters, e.g. chemical shifts, between the two lipoyl domains . The main structural differences between the two lipoyl domains occur in a solvent-exposed loop close in space to the lipoylation site. Des pite their high structural similarity, these lipoyl domains show a hig h preference for being reductively acylated by their parent Zero acid dehydrogenase. Potential residues of the lipoyl domain involved in thi s process of molecular recognition are discussed.