Streptococcus mutans, a facultatively aerobic and Gram-positive bacterium, is
the primary causative agent of dental caries and contributes to the multispecies
biofilm known as dental plaque. In this study, the aromatic-amino-acid
aminotransferase from Streptococcus mutans (SmAroAT) was recombinantly expressed
in Escherichia coli. An effective purification protocol was established. The
recombinant protein was crystallized using the hanging-drop vapor-diffusion
method with PEG 3350 as the primary precipitant. The crystal structure of
SmAroAT was solved at 2.2 Å resolution by the molecular-replacement method.
Structural analysis indicated that the proteins of the aromatic-amino-acid
aminotransferase family have conserved structural elements that might play a
role in substrate binding. These results may help in obtaining a better
understanding of the catabolism and biosynthesis of aromatic amino acids.
