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

Abstract

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 Δppe1 mutant shows increased tolerance to INH, accompanied by markedly reduced intracellular accumulation of INH compared with the wild-type strain. The Δppe1 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.