Structural intermediates observed only in intact Escherichia coli indicate a mechanism for TonB-dependent transport.
Elife
; 102021 07 12.
Article
in En
| MEDLINE
| ID: mdl-34251336
Bacteria must obtain nutrients from their surrounding environment in order to survive. In Gram-negative bacteria, proteins in the outer membrane surrounding the cell actively transport carbohydrates and trace nutrients like iron into the cell's interior. Although the structures of many of these transport proteins have been determined, the mechanism they use to move molecules across the membrane is poorly understood. To better understand this process, Nilaweera, Nyenhuis and Cafiso examined the structure of BtuB, a transport protein found in the outer membrane of Escherichia coli that is responsible for absorbing vitamin B12. Previous experiments analyzing the structure of BtuB, and other similar transporters, have been carried out on purified proteins that were extracted from the outer membrane. However, these isolated proteins fail to replicate the transport activity observed in bacterial cells. Nilaweera, Nyenhuis and Cafiso therefore wanted to see how the structure of BtuB changes when it is still enclosed in the membrane of E. coli. This revealed that BtuB undergoes large structural changes when it binds to vitamin B12, suggesting that this is an important part of the transport process. However, when purified BtuB was placed into an artificial membrane, these structural changes did not occur. This indicates that the cellular environment in the bacteria is needed for BtuB to carry out its transport role, and explains why previous experiments using purified proteins struggled to see this structural shift. This work highlights the importance of studying bacterial membrane proteins in their native cell environment. BtuB and similar transporters represent a large family of proteins unique to Gram-negative bacteria that have an impact on human health. Since these proteins are structurally alike, the results of this study may help resolve the transport mechanisms of other proteins, ultimately leading to new ways to control bacterial growth.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Membrane Transport Proteins
/
Bacterial Outer Membrane Proteins
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Escherichia coli Proteins
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Escherichia coli
/
Membrane Proteins
Limits:
Humans
Language:
En
Journal:
Elife
Year:
2021
Document type:
Article
Affiliation country:
United States
Country of publication:
United kingdom