A mycobacterial ABC transporter mediates the uptake of hydrophilic compounds

Nature. 2020 Apr;580(7803):409-412. doi: 10.1038/s41586-020-2072-8. Epub 2020 Mar 25.

Abstract

Mycobacterium tuberculosis (Mtb) is an obligate human pathogen and the causative agent of tuberculosis1-3. Although Mtb can synthesize vitamin B12 (cobalamin) de novo, uptake of cobalamin has been linked to pathogenesis of tuberculosis2. Mtb does not encode any characterized cobalamin transporter4-6; however, the gene rv1819c was found to be essential for uptake of cobalamin1. This result is difficult to reconcile with the original annotation of Rv1819c as a protein implicated in the transport of antimicrobial peptides such as bleomycin7. In addition, uptake of cobalamin seems inconsistent with the amino acid sequence, which suggests that Rv1819c has a bacterial ATP-binding cassette (ABC)-exporter fold1. Here, we present structures of Rv1819c, which reveal that the protein indeed contains the ABC-exporter fold, as well as a large water-filled cavity of about 7,700 Å3, which enables the protein to transport the unrelated hydrophilic compounds bleomycin and cobalamin. On the basis of these structures, we propose that Rv1819c is a multi-solute transporter for hydrophilic molecules, analogous to the multidrug exporters of the ABC transporter family, which pump out structurally diverse hydrophobic compounds from cells8-11.

MeSH terms

  • ATP-Binding Cassette Transporters / chemistry
  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Biological Transport
  • Bleomycin / metabolism*
  • Hydrophobic and Hydrophilic Interactions
  • Models, Molecular
  • Mycobacterium tuberculosis / chemistry
  • Mycobacterium tuberculosis / genetics
  • Mycobacterium tuberculosis / metabolism*
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary

Substances

  • ATP-Binding Cassette Transporters
  • Bacterial Proteins
  • Bleomycin