7SEE
Structure of E. coli LetB delta (Ring6) mutant, Ring1 in the closed state (Model 1)
Summary for 7SEE
| Entry DOI | 10.2210/pdb7see/pdb |
| EMDB information | 25066 |
| Descriptor | MCE family protein, Intermembrane transport protein YebT chimera, UNKNOWN ATOM OR ION (2 entities in total) |
| Functional Keywords | lipid transport, bacterial cell envelope, mce |
| Biological source | Escherichia coli More |
| Total number of polymer chains | 6 |
| Total formula weight | 473806.64 |
| Authors | Vieni, C.,Coudray, N.,Bhabha, G.,Ekiert, D. (deposition date: 2021-09-30, release date: 2022-02-09, Last modification date: 2024-06-05) |
| Primary citation | Vieni, C.,Coudray, N.,Isom, G.L.,Bhabha, G.,Ekiert, D.C. Role of Ring6 in the Function of the E. coli MCE Protein LetB. J.Mol.Biol., 434:167463-167463, 2022 Cited by PubMed Abstract: LetB is a tunnel-forming protein found in the cell envelope of some double-membraned bacteria, and is thought to be important for the transport of lipids between the inner and outer membranes. In Escherichia coli the LetB tunnel is formed from a stack of seven rings (Ring1 - Ring7), in which each ring is composed of a homo-hexameric assembly of MCE domains. The primary sequence of each MCE domain of the LetB protein is substantially divergent from the others, making each MCE ring unique in nature. The role of each MCE domain and how it contributes to the function of LetB is not well understood. Here we probed the importance of each MCE ring for the function of LetB, using a combination of bacterial growth assays and cryo-EM. Surprisingly, we find that ΔRing3 and ΔRing6 mutants, in which Ring3 and Ring6 have been deleted, confer increased resistance to membrane perturbing agents. Specific mutations in the pore-lining loops of Ring6 similarly confer increased resistance. A cryo-EM structure of the ΔRing6 mutant shows that despite the absence of Ring6, which leads to a shorter assembly, the overall architecture is maintained, highlighting the modular nature of MCE proteins. Previous work has shown that Ring6 is dynamic and in its closed state, may restrict the passage of substrate through the tunnel. Our work suggests that removal of Ring6 may relieve this restriction. The deletion of Ring6 combined with mutations in the pore-lining loops leads to a model for the tunnel gating mechanism of LetB. Together, these results provide insight into the functional roles of individual MCE domains and pore-lining loops in the LetB protein. PubMed: 35077766DOI: 10.1016/j.jmb.2022.167463 PDB entries with the same primary citation |
| Experimental method | ELECTRON MICROSCOPY (3.2 Å) |
Structure validation
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