| 1. |
- Ismail, Nurzian, et al.
(författare)
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Charge-driven dynamics of nascent-chain movement through the SecYEG translocon
- 2015
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Ingår i: Nature Structural & Molecular Biology. - : Springer Science and Business Media LLC. - 1545-9993 .- 1545-9985. ; 22:2, s. 145-149
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Tidskriftsartikel (refereegranskat)abstract
- On average, every fifth residue in secretory proteins carries either a positive or a negative charge. In a bacterium such as Escherichia coli, charged residues are exposed to an electric field as they transit through the inner membrane, and this should generate a fluctuating electric force on a translocating nascent chain. Here, we have used translational arrest peptides as in vivo force sensors to measure this electric force during cotranslational chain translocation through the SecYEG translocon. We find that charged residues experience a biphasic electric force as they move across the membrane, including an early component with a maximum when they are 47-49 residues away from the ribosomal P site, followed by a more slowly varying component. The early component is generated by the transmembrane electric potential, whereas the second may reflect interactions between charged residues and the periplasmic membrane surface.
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| 2. |
- Nilsson, Ola B., et al.
(författare)
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Cotranslational Protein Folding inside the Ribosome Exit Tunnel
- 2015
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Ingår i: Cell Reports. - : Elsevier BV. - 2211-1247. ; 12:10, s. 1533-1540
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Tidskriftsartikel (refereegranskat)abstract
- At what point during translation do proteins fold? It is well established that proteins can fold cotranslationally outside the ribosome exit tunnel, whereas studies of folding inside the exit tunnel have so far detected only the formation of helical secondary structure and collapsed or partially structured folding intermediates. Here, using a combination of co-translational nascent chain force measurements, inter-subunit fluorescence resonance energy transfer studies on single translating ribosomes, molecular dynamics simulations, and cryoelectron microscopy, we show that a small zinc-finger domain protein can fold deep inside the vestibule of the ribosome exit tunnel. Thus, for small protein domains, the ribosome itself can provide the kind of sheltered folding environment that chaperones provide for larger proteins.
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