Different conformations of nascent polypeptides during translocation across the ER membrane
<p>Abstract</p> <p>Background</p> <p>In eukaryotic cells, proteins are translocated across the ER membrane through a continuous ribosome-translocon channel. It is unclear to what extent proteins can fold already within the ribosome-translocon channel, and previous studi...
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doaj-44fbdaf8f4c94be7868d630e9985c3702020-11-24T20:52:15ZengBMCBMC Cell Biology1471-21212000-12-0111310.1186/1471-2121-1-3Different conformations of nascent polypeptides during translocation across the ER membraneWhitley PaulNilsson IngMarieMingarro Ismaelvon Heijne Gunnar<p>Abstract</p> <p>Background</p> <p>In eukaryotic cells, proteins are translocated across the ER membrane through a continuous ribosome-translocon channel. It is unclear to what extent proteins can fold already within the ribosome-translocon channel, and previous studies suggest that only a limited degree of folding (such as the formation of isolated α-helices) may be possible within the ribosome.</p> <p>Results</p> <p>We have previously shown that the conformation of nascent polypeptide chains in transit through the ribosome-translocon complex can be probed by measuring the number of residues required to span the distance between the ribosomal P-site and the lumenally disposed active site of the oligosaccharyl transferase enzyme (J. Biol. Chem 271: 6241-6244).Using this approach, we now show that model segments composed of residues with strong helix-forming properties in water (Ala, Leu) have a more compact conformation in the ribosome-translocon channel than model segments composed of residues with weak helix-forming potential (Val, Pro).</p> <p>Conclusions</p> <p>The main conclusions from the work reported here are (i) that the propensity to form an extended or more compact (possibly α-helical) conformation in the ribosome-translocon channel does not depend on whether or not the model segment has stop-transfer function, but rather seems to reflect the helical propensities of the amino acids as measured in an aqueous environment, and (ii) that stop-transfer sequences may adopt a helical structure and integrate into the ER membrane at different times relative to the time of glycan addition to nearby upstream glycosylation acceptor sites.</p> http://www.biomedcentral.com/1471-2121/1/3 |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Whitley Paul Nilsson IngMarie Mingarro Ismael von Heijne Gunnar |
spellingShingle |
Whitley Paul Nilsson IngMarie Mingarro Ismael von Heijne Gunnar Different conformations of nascent polypeptides during translocation across the ER membrane BMC Cell Biology |
author_facet |
Whitley Paul Nilsson IngMarie Mingarro Ismael von Heijne Gunnar |
author_sort |
Whitley Paul |
title |
Different conformations of nascent polypeptides during translocation across the ER membrane |
title_short |
Different conformations of nascent polypeptides during translocation across the ER membrane |
title_full |
Different conformations of nascent polypeptides during translocation across the ER membrane |
title_fullStr |
Different conformations of nascent polypeptides during translocation across the ER membrane |
title_full_unstemmed |
Different conformations of nascent polypeptides during translocation across the ER membrane |
title_sort |
different conformations of nascent polypeptides during translocation across the er membrane |
publisher |
BMC |
series |
BMC Cell Biology |
issn |
1471-2121 |
publishDate |
2000-12-01 |
description |
<p>Abstract</p> <p>Background</p> <p>In eukaryotic cells, proteins are translocated across the ER membrane through a continuous ribosome-translocon channel. It is unclear to what extent proteins can fold already within the ribosome-translocon channel, and previous studies suggest that only a limited degree of folding (such as the formation of isolated α-helices) may be possible within the ribosome.</p> <p>Results</p> <p>We have previously shown that the conformation of nascent polypeptide chains in transit through the ribosome-translocon complex can be probed by measuring the number of residues required to span the distance between the ribosomal P-site and the lumenally disposed active site of the oligosaccharyl transferase enzyme (J. Biol. Chem 271: 6241-6244).Using this approach, we now show that model segments composed of residues with strong helix-forming properties in water (Ala, Leu) have a more compact conformation in the ribosome-translocon channel than model segments composed of residues with weak helix-forming potential (Val, Pro).</p> <p>Conclusions</p> <p>The main conclusions from the work reported here are (i) that the propensity to form an extended or more compact (possibly α-helical) conformation in the ribosome-translocon channel does not depend on whether or not the model segment has stop-transfer function, but rather seems to reflect the helical propensities of the amino acids as measured in an aqueous environment, and (ii) that stop-transfer sequences may adopt a helical structure and integrate into the ER membrane at different times relative to the time of glycan addition to nearby upstream glycosylation acceptor sites.</p> |
url |
http://www.biomedcentral.com/1471-2121/1/3 |
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