Elongation of the Poly-?-glutamate Tail of F420 Requires Both Domains of the F420:?-Glutamyl Ligase (FbiB) of Mycobacterium tuberculosis.

ABSTRACT: Cofactor F420is an electron carrier with a major role in the oxidoreductive reactions ofMycobacterium tuberculosis, the causative agent of tuberculosis. A ?-glutamyl ligase catalyzes the final steps of the F420biosynthesis pathway by successive additions ofl-glutamate residues to F420-0, producing a poly-?-glutamate tail. The enzyme responsible for this reaction in archaea (CofE) comprises a single domain and produces F420-2 as the major species. The homologousM. tuberculosisenzyme, FbiB, is a two-domain protein and produces F420with predominantly 5-7l-glutamate residues in the poly-?-glutamate tail. The N-terminal domain of FbiB is homologous to CofE with an annotated ?-glutamyl ligase activity, whereas the C-terminal domain has sequence similarity to an FMN-dependent family of nitroreductase enzymes. Here we demonstrate that full-length FbiB adds multiplel-glutamate residues to F420-0in vitroto produce F420-5 after 24 h; communication between the two domains is critical for full ?-glutamyl ligase activity. We also present crystal structures of the C-terminal domain of FbiB in apo-, F420-0-, and FMN-bound states, displaying distinct sites for F420-0 and FMN ligands that partially overlap. Finally, we discuss the features of a full-length structural model produced by small angle x-ray scattering and its implications for the role of N- and C-terminal domains in catalysis.

SUBMITTER: Bashiri G 

PROVIDER: S-EPMC4807274 | biostudies-literature | 2016 Mar

REPOSITORIES: biostudies-literature