A voltage-gated porin PPE1 regulates secretion and drug resistance in Mycobacterium tuberculosis

Drug resistance in Mycobacterium tuberculosis ( Mtb ) remains a formidable clinical hurdle, compounded by the fact that the pathways by which antibiotics penetrate its multilayered cell envelope remain incompletely mapped. We identify PPE1 as a voltage-gated outer-membrane porin that mediates the secretion of kupyaphores while also facilitating the uptake of the frontline anti-tubercular drug isoniazid (INH). Genome-wide association analysis of 38,038 clinical isolates links ppe1 mutations with INH resistance, highlighting its clinical relevance. Consistent with this, the Mtb Δ ppe1 mutant shows increased tolerance to INH, accompanied by markedly reduced intracellular accumulation of INH compared with the wild-type strain. The Δ ppe1 strain exhibits attenuated infection, impaired growth, and reduced virulence in a murine infection model. Electron microscopy, molecular modeling, and single-channel electrophysiology reveal that PPE1 assembles into an unusual pentameric α-helical channel, distinct from classical β-barrel bacterial porins. Together, our findings identify PPE1 as a key determinant of mycobacterial membrane permeability that coordinates metallophore secretion and also antibiotic influx. This work uncovers a previously unrecognized mechanism governing Mtb physiology, virulence, and drug susceptibility, providing a potential target for therapeutic intervention.