Search

Malaria, a devastating parasitic infection, is the leading cause of death in many developing countries. Unfortunately, the most deadliest causative agent of malaria, Plasmodium falciparum , has developed resistance to nearly all currently available antimalarial drugs. The P. falciparum Niemann-Pick type C1-related (PfNCR1) transporter has been identified as a druggable target, but its structure and detailed molecular mechanism are not yet available. Here, we present three structures of PfNCR1 with and without the functional inhibitor MMV009108 at resolutions between 2.98 and 3.81 Å using single-particle cryo-electron microscopy (cryo-EM), suggesting that PfNCR1 binds cholesterol and forms a cholesterol transport tunnel to modulate the composition of the parasite plasma membrane. Cholesterol efflux assays show that PfNCR1 is an exporter capable of extruding cholesterol from the membrane. Additionally, the inhibition mechanism of MMV009108 appears to be due to a direct blockage of PfNCR1, preventing this transporter from shuttling cholesterol.

Mycobacterium tuberculosis , the causative agent of the airborne infection tuberculosis (TB), contains 13 mycobacterial membrane protein large (MmpL) transporters that can be divided into two distinct subclasses. These MmpL proteins play important functional roles within the mycobacterium and subsequently are considered attractive drug targets to combat TB infection. Previously, we reported both X-ray and cryo-electron microscopy (cryo-EM) structures of the MmpL3 transporter, providing high-resolution structural information for this subclass of the MmpL proteins. Thus far, there is no structural information available for the other subclass, which includes MmpL5, an inner membrane transporter that plays a critical role in iron hemostasis. Here, we report the first cryo-EM structure of the Mycobacterium smegmatis MmpL5 transporter bound with the meromycolate extension acyl carrier protein M (AcpM) to a resolution of 2.81 Å. Our structural data reveals that MmpL5 and AcpM interact in the cytoplasm to form a complex, and this allows us to propose that MmpL5 may also associate with the mycobactin L (MbtL) protein in a similar fashion to form a heterocomplex important for iron acquisition, which enables the survival and replication of the mycobacterium., Importance: The emergence and spread of multidrug-resistant tuberculosis (TB) present enormous challenges to the global public health. The causative agent, Mycobacterium tuberculosis , has now infected more than one-third of the world's population. Here, we report the first structure of the mycobacterial membrane protein large 5 (MmpL5), an essential transporter for iron acquisition, bound with the meromycolate extension acyl carrier protein M (AcpM), indicating a plausible pathway for mycobactin translocation. Our studies will ultimately inform an era in structure-guided drug design to combat TB infection., Competing Interests: The authors declare no conflict of interest.

The Mycobacterium tuberculosis (Mtb) pathogen, the causative agent of the airborne infection tuberculosis (TB), harbors a number of mycobacterial membrane protein large (MmpL) transporters. These membrane proteins can be separated into 2 distinct subclasses, where they perform important functional roles, and thus, are considered potential drug targets to combat TB. Previously, we reported both X-ray and cryo-EM structures of the MmpL3 transporter, providing high-resolution structural information for this subclass of the MmpL proteins. Currently, there is no structural information available for the subclass associated with MmpL4 and MmpL5, transporters that play a critical role in iron homeostasis of the bacterium. Here, we report cryo-EM structures of the M. smegmatis MmpL4 and MmpL5 transporters to resolutions of 2.95 Å and 3.00 Å, respectively. These structures allow us to propose a plausible pathway for siderophore translocation via these 2 transporters, an essential step for iron acquisition that enables the survival and replication of the mycobacterium., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Maharjan et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)