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Topogenesis of heterologously expressed fragments of the human Y4 GPCR


Marino, J; Geertsma, E R; Zerbe, O (2012). Topogenesis of heterologously expressed fragments of the human Y4 GPCR. Biochimica et Biophysica Acta (BBA) - Biomembranes, 1818(12):3055-3063.

Abstract

Fragments of large membrane proteins have the potential to facilitate structural analysis by NMR, but their folding state remains a concern. Here we determined the quality of folding upon heterologous expression for a series of N- or C-terminally truncated fragments of the human Y4 G-protein coupled receptor, amounting to six different complementation pairs. As the individual fragments lack a specific function that could be used to ascertain proper folding, we instead assessed folding on a basic level by studying their membrane topology and by comparing it to well-established structural models of GPCRs. The topology of the fragments was determined using a reporter assay based on C-terminal green fluorescent protein- or alkaline phosphatase-fusions. N-terminal fusions to Lep or Mistic were used if a periplasmic orientation of the N-terminus of the fragments was expected based on predictions. Fragments fused to Mistic expressed at comparably high levels, whereas Lep fusions were produced to a much lower extent. Though none of the fragments exclusively adopted one orientation, often the correct topology predominated. In addition, systematic analysis of the fragment series suggested that the C-terminal half of the Y4 receptor is more important for adopting the correct topology than the N-terminal part. Using the detergent dodecylphosphocholine, selected fragments were solubilized from the membrane and proved sufficiently stable to allow purification. Finally, as a first step toward reconstituting a functional receptor from two fragments, we observed a physical interaction between complementing fragments pairs upon co-expression.

Abstract

Fragments of large membrane proteins have the potential to facilitate structural analysis by NMR, but their folding state remains a concern. Here we determined the quality of folding upon heterologous expression for a series of N- or C-terminally truncated fragments of the human Y4 G-protein coupled receptor, amounting to six different complementation pairs. As the individual fragments lack a specific function that could be used to ascertain proper folding, we instead assessed folding on a basic level by studying their membrane topology and by comparing it to well-established structural models of GPCRs. The topology of the fragments was determined using a reporter assay based on C-terminal green fluorescent protein- or alkaline phosphatase-fusions. N-terminal fusions to Lep or Mistic were used if a periplasmic orientation of the N-terminus of the fragments was expected based on predictions. Fragments fused to Mistic expressed at comparably high levels, whereas Lep fusions were produced to a much lower extent. Though none of the fragments exclusively adopted one orientation, often the correct topology predominated. In addition, systematic analysis of the fragment series suggested that the C-terminal half of the Y4 receptor is more important for adopting the correct topology than the N-terminal part. Using the detergent dodecylphosphocholine, selected fragments were solubilized from the membrane and proved sufficiently stable to allow purification. Finally, as a first step toward reconstituting a functional receptor from two fragments, we observed a physical interaction between complementing fragments pairs upon co-expression.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Department of Biochemistry
07 Faculty of Science > Department of Biochemistry

07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:570 Life sciences; biology
540 Chemistry
Uncontrolled Keywords:GPCR heterologous expression topogenesis membrane proteins
Language:English
Date:2012
Deposited On:12 Sep 2012 08:43
Last Modified:05 Apr 2016 15:56
Publisher:Elsevier
ISSN:0005-2736
Funders:Swiss National Science Foundation
Publisher DOI:https://doi.org/10.1016/j.bbamem.2012.07.023
PubMed ID:22867850

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