Journal:FEBS Open Bio:1: Difference between revisions

Previous structures have shown defined ‘open’ and ‘closed’ states of the B-domain (Fig. 2) <ref>pmid 19213731</ref><ref>pmid 7915138</ref>[40,43]. In addition, the biotin carboxylase domain of pyruvate carboxylase from ''Bacillus thermodenitrificans'' displays what appears to be an intermediate, but defined, conformation <ref>pmid 17642515</ref>[44]. In the current structure, however, while protomer A represents the previously observed ‘closed’ state, protomer B represent a different structural state where no conformation is present in high enough occupancy to be possible to reliably model. Based on the location of the segment of positive difference density relative to protomer B, it is, however, clear that the location of the B-domain in the partially occupied structural state that gives rise to this density is not the same as either the previously described ‘closed’ or ‘open’ states. Rather, the density suggests an even more extended conformation of the B-domain relative to the rest of the protein (Fig. 2). Together, the most likely interpretation of the combined structural data of biotin-dependent carboxylases is that the B-domain is dynamic over a continuum of conformations, or several defined conformations.