QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online 27 May 2003
doi: 10.1242/jcs.00597

This Article Figures Only Full Text Full Text (PDF) All Versions of this Article: jcs.00597v1 116/14/2875    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Römisch, K. Articles by Cheng, C.-H. C. Search for Related Content PubMed PubMed Citation Articles by Römisch, K. Articles by Cheng, C.-H. C.

Protein translocation across the endoplasmic reticulum membrane in cold-adapted organisms

¹ University of Cambridge, CIMR and Department of Clinical Biochemistry, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 2XY, UK
² Department of Animal Biology, University of Illinois at Urbana-Champaign, IL 61801, USA

^* Author for correspondence (e-mail: kbr20{at}cam.ac.uk)

Accepted 4 April 2003

Secretory proteins enter the secretory pathway by translocation across the membrane of the endoplasmic reticulum (ER) via a channel formed primarily by the Sec61 protein. Protein translocation is highly temperature dependent in mesophilic organisms. We asked whether the protein translocation machinery of organisms from extremely cold habitats was adapted to function at low temperature and found that post-translational protein import into ER-derived microsomes from Antarctic yeast at low temperature was indeed more efficient than into mesophilic yeast microsomes. Analysis of the amino-acid sequences of the core component of the protein translocation channel, Sec61p, from Antarctic yeast species did not reveal amino-acid changes potentially adaptive for function in the cold, because the sequences were too divergent. We therefore analyzed Sec61 (vertebrate Sec61p) sequences and protein translocation into the ER of Antarctic and Arctic fishes and compared them to Sec61 and protein translocation into the ER of temperate-water fishes and mammals. Overall, Sec61 is highly conserved amongst these divergent taxa; a number of amino-acid changes specific to fishes are evident throughout the protein, and, in addition, changes specific to cold-water fishes cluster in the lumenal loop between transmembrane domains 7 and 8 of Sec61, which is known to be important for protein translocation across the ER membrane. Secretory proteins translocated more efficiently into fish microsomes than into mammalian microsomes at 10°C and 0°C. The efficiency of protein translocation at 0°C was highest for microsomes from a cold-water fish. Despite substantial differences in ER membrane lipid composition, ER membrane fluidity was identical in Antarctic fishes, mesophilic fishes and warm-blooded vertebrates, suggesting that membrane fluidity, although typically important for the function of the transmembrane proteins, is not limiting for protein translocation across the ER membrane in the cold. Collectively, our data suggest that the limited amino-acid changes in Sec61 from fishes may be functionally significant and represent adaptive changes that enhance channel function in the cold.

Key words: Sec61 channel, ER lipid composition, Secretion, Antarctic fish, Antarctic yeast

This article has been cited by other articles:

				Z. Chen, C.-H. C. Cheng, J. Zhang, L. Cao, L. Chen, L. Zhou, Y. Jin, H. Ye, C. Deng, Z. Dai, et al. Transcriptomic and genomic evolution under constant cold in Antarctic notothenioid fish PNAS, September 2, 2008; 105(35): 12944 - 12949. [Abstract] [Full Text] [PDF]

				A. J. Kiss, A. Y. Mirarefi, S. Ramakrishnan, C. F. Zukoski, A. L. DeVries, and C.-H. C. Cheng Cold-stable eye lens crystallins of the Antarctic nototheniid toothfish Dissostichus mawsoni Norman J. Exp. Biol., December 15, 2004; 207(26): 4633 - 4649. [Abstract] [Full Text] [PDF]