Secondary structure of beta-hydroxydecanoyl thiol ester dehydrase, a 39-kDa protein, derived from H alpha, C alpha, C beta and CO signal assignments and the Chemical Shift Index: comparison with the crystal structure.

Nearly complete backbone 1H, 15N and 13C signal assignments are reported for beta-hydroxydecanoyl thiol ester dehydrase, a 39-kDa homodimer containing 342 amino acids. Although 15N relaxation data show that the protein has a rotational correlation time of 18 ns, assignments were derived from triple-resonance experiments recorded at 500 MHz and pH 6.8, without deuteration. The Chemical Shift Index, CSI, identified two long helices and numerous beta-strands in dehydrase. The CSI predictions are in close agreement with the secondary structure identified in the recently derived crystal structure, particularly when one takes account of the numerous bulges in the beta-strands. The assignment of dehydrase and a large deuterated protein [Yamazaki et al. (1994) J. Am. Chem. Soc., 116, 11655-11666] suggest that assignment of 40-60 kDa proteins is feasible. Hence, further progress in understanding the chemical shift/structure relationship could open the way to determine the structures of such large proteins.