PT  - JOURNAL ARTICLE
AU  - Chen, James
AU  - Fruhauf, Alice
AU  - Fan, Catherine
AU  - Ponce, Jackeline
AU  - Ueberheide, Beatrix
AU  - Bhabha, Gira
AU  - Ekiert, Damian C.
TI  - Structure of an endogenous mycobacterial MCE lipid transporter
AID  - 10.1101/2022.12.08.519548
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.12.08.519548
4099  - http://biorxiv.org/content/early/2022/12/08/2022.12.08.519548.short
4100  - http://biorxiv.org/content/early/2022/12/08/2022.12.08.519548.full
AB  - Mycobacterium tuberculosis (Mtb) infects human macrophages, where it scavenges nutrients for survival. The Mammalian Cell Entry (MCE) proteins are important virulence factors implicated in import of nutrients such as fatty acids from the host, but their structures and mechanisms remain unknown. Here we report the high-resolution structure of the endogenous Mce1 transporter from Mycobacterium smegmatis, a non-pathogenic relative of Mtb. Ten distinct proteins assemble into an elongated complex, long enough to span the cell envelope. A unique helical needle creates a curved hydrophobic tunnel for lipid transport across the periplasm. Combining cryo-EM and AlphaFold2, we identify a previously unknown subunit of the Mce1 complex, which we name LucB. Our data lead to a structural model for Mce1-mediated fatty acid import in mycobacteria.One-sentence Summary Cryo-EM structure reveals how a major mycobacterial virulence factor, Mce1, assembles to transport fatty acids across the cell envelope.Competing Interest StatementThe authors have declared no competing interest.