l , l -diaminopimelate aminotransferase, a trans-kingdom enzyme shared by Chlamydia and plants for synthesis of diaminopimelate/lysine

The synthesis ofmeso -diaminopimelic acid (m -DAP) in bacteria is essential for both peptidoglycan and lysine biosynthesis. From genome sequencing data, it was unclear how bacteria of the Chlamydiales order would synthesizem -DAP in the absence ofdapD ,dapC , anddapE , which are missing from the genome. Here, we assessed the biochemical capacity ofChlamydia trachomatis serovar L2 to synthesizem -DAP. Expression of the chlamydialasd ,dapB , anddapF genes in the respectiveEscherichia coli m -DAP auxotrophic mutants restored the mutants to DAP prototrophy. Screening of aC. trachomatis genomic library in anE. coli ΔdapD DAP auxotroph identifiedct390 as encoding an enzyme that restored growth to theEscherichia coli mutant.ct390 also was able to complement anE. coli ΔdapD ΔdapE , but not a ΔdapD ΔdapF mutant, providing genetic evidence that it encodes an aminotransferase that may directly convert tetrahydrodipicolinate tol ,l -diaminopimelic acid. This hypothesis was supported byin vitro kinetic analysis of the CT390 protein and the fact that similar properties were demonstrated for theProtochlamydia amoebophila homologue, PC0685.In vivo , theC. trachomatis m -DAP synthesis genes are expressed as early as 8 h after infection. An aminotransferase activity analogous to CT390 recently has been characterized in plants and cyanobacteria. This previously undescribed pathway form -DAP synthesis supports an evolutionary relationship among the chlamydiae, cyanobacteria, and plants and strengthens the argument that chlamydiae synthesize a cell wall despite the inability of efforts to date to detect peptidoglycan in these organisms.