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The work Sinothai Poen published as part of his recent PhD has been chosen as the cover of the journal Biochemical Journal this month. Sinothai did his PhD with Professor Kurt Krause, and has since returned to Thailand to take up a lecturing position.
Exploring the Structure of Glutamate Racemase from Mycobacterium tuberculosis as a Template for Anti-mycobacterial Drug Discovery.
Sinothai Poen, Yoshio Nakatani, Helen K Opel-Reading, Mortiz Lassé, Renwick C J Dobson, and Kurt L Krause.
Glutamate racemase (MurI) is responsible for providing D-glutamate for peptidoglycan biosynthesis in bacteria and has been a favored target in pharmaceutical drug design efforts. It has recently been proven to be essential in M. tuberculosis, a disease for which new medications are urgently needed. In this study, we have determined the protein crystal structures of MurI from both M. tuberculosis and M. smegmatis in complex with D-glutamate to 2.3 Å and 1.8 Å, respectively. These structures are conserved, but reveal differences in their active site architecture compared to that of other MurI structures. Furthermore, compounds designed to target other glutamate racemases have been screened and do not inhibit mycobacterial MurI, suggesting that a new drug design effort will be needed to develop inhibitors. A new type of MurI dimer arrangement has been observed in both structures, and this arrangement becomes the third biological dimer geometry for MurI found to date. The mycobacterial MurI dimer is tightly associated with a KD in the nanomolar range. The enzyme binds D- and L-glutamate specifically, but is inactive in solution unless the dimer interface is mutated. We created triple mutants of this interface in the M. smegmatis glutamate racemase (D26R/R105A/G194R or E) that have appreciable activity (kcat = 0.056-0.160 min-1 and KM = 0.26-0.51 mM) and can be utilized to screen proposed antimicrobial candidates for inhibition.
Biochem J, 2016 vol. 473 (9) pp. 1267-1280.