Mycobacterium bovis BCG dodecin gene codes a functional protein despite of a start codon mutation

Abstract

Dodecin is a dodecamer involved in flavin homeostasis, with interesting temperature and osmolarity endurance features in Mycobacterium tuberculosis. A single nucleotide polymorphism in the gene's start codon in BCG, converting ATG to ACG, is predicted to generate a N-terminal shorter isoform, lacking the first 7 amino acids. We previously reported that the shortened recombinant protein has reduced extremophilic features. Here we investigate if within the mycobacterial context dodecin can be produced from both alleles, carrying ATG and ACG start codons. Reporter gene assays using mcherry cloned downstream and in phase to both M.tb and BCG "upstream" regions confirms production of functional proteins. Complementation with both dod alleles similarly enhances M. smegmatis growth after entry into logarithmic phase and exposure to hydrogen peroxide, possibly implicating this protein in oxidative stress response mechanisms. Altogether these data indicate that BCG dodecin is indeed produced, notwithstanding in lower levels compared to M.tb, conferring similar phenotypes, even with the SNP altering the M.tb ATG start codon to the BCG ACG. This protein might be an interesting drug target for the development of new therapeutics against tuberculosis.

Keywords: BCG vaccine; Dodecin; Flavin binding protein; Mycobacterium bovis BCG Moreau; Mycobacterium tuberculosis.