The three-dimensional structure of diaminopimelate decarboxylase from Mycobacterium tuberculosis reveals a tetrameric enzyme organisation.
The three-dimensional structure of the enzyme diaminopimelate decarboxylase from
Mycobacterium tuberculosis has been determined in a new crystal form and refined
to a resolution of 2.33 A. The monoclinic crystals contain one tetramer
exhibiting D(2)-symmetry in the asymmetric unit. The tetramer exhibits a
donut-like structure with a hollow interior. All four active sites are
accessible only from the interior of the tetrameric assembly. Small-angle X-ray
scattering indicates that in solution the predominant oligomeric species of the
protein is a dimer, but also that higher oligomers exist at higher protein
concentrations. The observed scattering data are best explained by assuming a
dimer-tetramer equilibrium with about 7% tetramers present in solution.
Consequently, at the elevated protein concentrations in the crowded environment
inside the cell the observed tetramer may constitute the biologically relevant
functional unit of the enzyme.