3-DIMENSIONAL STRUCTURE OF TETRAHYDRODIPICOLINATE N-SUCCINYLTRANSFERASE

The conversion of tetrahydrodipicolinate and succinyl-CoA to N-succiny ltetrahydrodipicolinate and CoA is catalyzed by tetrahydrodipicolinate N-succinyltransferase and is the committed step in the succinylase pa thway by which bacteria synthesize L-lysine and meso-diaminopimelate, a component of peptidoglycan. The X-ray crystal structure of THDP succ inyltransferase has been determined to 2.2 Angstrom resolution and has been refined to a crystallographic R-factor of 17.0%, The enzyme is t rimeric and displays the left-handed parallel beta-helix (L beta H) st ructural motif encoded by the ''hexapeptide repeat'' amino acid sequen ce motif [Raetz, C. R, H., & Roderick, S. L. (1995) Science 270, 997-1 000]. The approximate location of the active site of THDP succinyltran sferase is suggested by the proximity of binding sites for two inhibit ors; p-(chloromercuri)benzenesulfonic acid and cobalt ion, both of whi ch bind to the L beta H domain.