Elucidation of the bicarbonate binding site and insights into the carboxylation mechanism of (N⁵)-carboxyaminoimidazole ribonucleotide synthase (PurK) from Bacillus anthracis

The first structure of B. anthracis PurK with a bicarbonate ion in the active site is reported. Based on several enzyme structures with different ligands in the active site, a mechanism for the enzymatic reaction is proposed.

Structures of SAICAR synthetase (PurC) from Streptococcus pneumoniae with ADP, Mg²⁺, AIR and Asp

The structure of SAICAR synthetase from S. pneumoniae had been solved in complex with ADP, Asp, Mg²⁺ and AIR. The newly defined binding site for Asp provides information about the mechanism.