Diisonitrile Chalkophore Structure and Function in Mycobacterial Copper Acquisition

We confirmed that a short-chain analogue of the natural products binds tightly to Cu(I) and Cu(II), but not Zn(II), and estimated its Cu(I) binding affinity. We then used these analogues to probe the impacts of diisonitrile acyl chain length, amino acid backbone, and C-terminal motif on the rescue of M. tuberculosis and Mycobacterium marinum growth in copper-restricted conditions. The observed structural preferences align with current knowledge of the corresponding natural product structures in these bacteria, but both species also exhibited surprising flexibility in accepting diverse diisonitrile analogues for this function.

This work provides new insights into the structural features of diisonitrile chalkophores required for function in mycobacterial copper homeostasis, and the distinct structural preferences between species, while suggesting some structural plasticity in their cellular copper acquisition systems.