Mycobacterial resistance to zinc poisoning requires assembly of P-ATPase-containing membrane metal efflux platforms

ABSTRACT Transition metals are toxic at high concentrations. The P 1B -ATPase metal exporter CtpC/Rv3270 is required for resistance to zinc poisoning in the human pathogen Mycobacterium tuberculosis . Here, we discovered that zinc resistance also depends on the chaperone-like protein PacL1/Rv3269. PacL1 bound Zn 2+ , but unlike PacL1 and CtpC, the PacL1 metal-binding motif (MBM) was required only at high zinc concentrations. PacL1 co-localized with CtpC in dynamic microdomains within the mycobacterial plasma membrane. Microdomain formation did not require flotillins nor the PacL1 MBM. Instead, loss of the PacL1 Glutamine/Alanine repeats led to loss of CtpC and sensitivity to zinc. PacL1 and CtpC are within the same operon, and homologous PacL1-P 1B -ATPase pairs are widely distributed within and across prokaryotes. PacL1 colocalized and functioned redundantly with PacL orthologs in Mycobacterium tuberculosis . Overall, our study suggests that PacL proteins are scaffolds that assemble P-ATPase-containing metal efflux platforms, a novel type of functional membrane microdomain that underlies bacterial resistance to metal poisoning.