NMR studies on the 46-kDa dimeric protein, 3,4-dihydroxy-2-butanone 4-phosphate synthase, using 2H, 13C, and 15N-labelling

3,4-Dihydroxy-2-butanone 4-phosphate synthase catalyses the release of C-4 from the substrate, ribulose phosphate, via a complex series of rearrangement reactions. The cognate ribB gene of Escherichia coli was hyperexpressed in a recombinant E. coli strain. The protein was shown to be a 46-kDa homodimer by hydrodynamic analysis. A variety of protein samples labelled with different grades of C-13, N-15 and H-2, i.e, one with 100% H-2 and N-15, one with 75% H-2, 99% C-13,N-15, and one with 100% H-2, 99% C-13,N-15 were prepared. Despite the large molecular size, 2- and 3-dimensional NMR spectra of reasonable quality were obtained. Attempts at the assignment of individual C-13, N-15 and H-1 signals show, in principle, the feasibility of structure determination. The number of NMR signals shows unequivocally that the homodimeric protein obeys strict C-2 symmetry.