7AI2

Crystal structure of Se-Met labelled MCE domain of Mce4A from Mycobacterium tuberculosis H37Rv

Summary for 7AI2

• Entry DOI: 10.2210/pdb7ai2/pdb
• Descriptor: Mce-family protein Mce4A (1 entity in total)
• Functional Keywords: susbtrate binding protein, mce, mce4a, transport protein
• Biological source: Mycobacterium tuberculosis H37Rv
• Total number of polymer chains: 4
• Total formula weight: 61346.34

Authors

Asthana, P.,Venkatesan, R. (deposition date: 2020-09-25, release date: 2021-08-25, Last modification date: 2021-10-13)

Primary citation

Asthana, P.,Singh, D.,Pedersen, J.S.,Hynonen, M.J.,Sulu, R.,Murthy, A.V.,Laitaoja, M.,Janis, J.,Riley, L.W.,Venkatesan, R.
Structural insights into the substrate-binding proteins Mce1A and Mce4A from Mycobacterium tuberculosis .
Iucrj, 8:757-774, 2021

PubMed Abstract: (), which is responsible for more than a million deaths annually, uses lipids as the source of carbon and energy for its survival in the latent phase of infection. cannot synthesize all of the lipid molecules required for its growth and pathogenicity. Therefore, it relies on transporters such as the mammalian cell entry (Mce) complexes to import lipids from the host across the cell wall. Despite their importance for the survival and pathogenicity of , information on the structural properties of these proteins is not yet available. Each of the four Mce complexes in (Mce1-4) comprises six substrate-binding proteins (SBPs; MceA-F), each of which contains four conserved domains (N-terminal transmembrane, MCE, helical and C-terminal unstructured tail domains). Here, the properties of the various domains of Mce1A and Mce4A, which are involved in the import of mycolic/fatty acids and cholesterol, respectively, are reported. In the crystal structure of the MCE domain of Mce4A (MtMce4A) a domain-swapped conformation is observed, whereas solution studies, including small-angle X-ray scattering (SAXS), indicate that all Mce1A and Mce4A domains are predominantly monomeric. Further, structural comparisons show interesting differences from the bacterial homologs MlaD, PqiB and LetB, which form homohexamers when assembled as functional transporter complexes. These data, and the fact that there are six SBPs in each operon, suggest that the MceA-F SBPs from Mce1-4 may form heterohexamers. Also, interestingly, the purification and SAXS analysis showed that the helical domains interact with the detergent micelle, suggesting that when assembled the helical domains of MceA-F may form a hydrophobic pore for lipid transport, as observed in EcPqiB. Overall, these data highlight the unique structural properties of the Mce SBPs.

PubMed: 34584737
DOI: 10.1107/S2052252521006199

Experimental method

X-RAY DIFFRACTION (3.61 Å)