Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Insertion of marginally hydrophobic helix in EmrD
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.ORCID iD: 0000-0002-6176-7788
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

The positive inside rule governs the orientation of membrane proteins in such a way that more positively chargedamino acids are found on the inside of a cell. The exact mechanisms of how this is achieved are not well known, butit is clear that positively charged residues can facilitate the insertion of transmembrane helices that are not sufficientlyhydrophobic to be inserted otherwise. Here, we study one such helix, helix 2 in EmrD. We show that the insertionof this helix is facilitated when followed by positively charged residues and a hydrophobic helix. Surprisingly thepositively charged residues are not sufficient alone. This further strengthens our earlier observations that the last helixneeds to be more hydrophobic than previous helices.

Place, publisher, year, edition, pages
2014.
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
URN: urn:nbn:se:su:diva-108912OAI: oai:DiVA.org:su-108912DiVA: diva2:763802
Available from: 2014-11-17 Created: 2014-11-06 Last updated: 2016-05-27Bibliographically approved
In thesis
1. Marginally hydrophobic transmembrane α-helices shaping membrane protein folding
Open this publication in new window or tab >>Marginally hydrophobic transmembrane α-helices shaping membrane protein folding
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Most membrane proteins are inserted into the membrane co-translationally utilizing the translocon, which allows a sufficiently long and hydrophobic stretch of amino acids to partition into the membrane. However, X-ray structures of membrane proteins have revealed that some transmembrane helices (TMHs) are surprisingly hydrophilic. These marginally hydrophobic transmembrane helices (mTMH) are not recognized as TMHs by the translocon in the absence of local sequence context.

We have studied three native mTMHs, which were previously shown to depend on a subsequent TMH for membrane insertion. Their recognition was not due to specific interactions. Instead, the presence of basic amino acids in their cytoplasmic loop allowed membrane insertion of one of them. In the other two, basic residues are not sufficient unless followed by another, hydrophobic TMH. Post-insertional repositioning are another way to bring hydrophilic residues into the membrane. We show how four long TMHs with hydrophilic residues seen in X-ray structures, are initially inserted as much shorter membrane-embedded segments. Tilting is thus induced after membrane-insertion, probably through tertiary packing interactions within the protein.

Aquaporin 1 illustrates how a mTMH can shape membrane protein folding and how repositioning can be important in post-insertional folding. It initially adopts a four-helical intermediate, where mTMH2 and TMH4 are not inserted into the membrane. Consequently, TMH3 is inserted in an inverted orientation. The final conformation with six TMHs is formed by TMH2 and 4 entering the membrane and TMH3 rotating 180°. Based on experimental and computational results, we propose a mechanism for the initial step in the folding of AQP1: A shift of TMH3 out from membrane core allows the preceding regions to enter the membrane, which provides flexibility for TMH3 to re-insert in its correct orientation.

Place, publisher, year, edition, pages
Stockholm: Department of biochemistry and biophysics, Stockholm University, 2014. 66 p.
Keyword
membrane protein folding, hydrophobicity, translocon, transmembrane helix, marginally hydrophobic transmembrane helices, orientational preference, positive inside rule, aquaporin 1
National Category
Biochemistry and Molecular Biology
Research subject
Biochemistry
Identifiers
urn:nbn:se:su:diva-109335 (URN)978-91-7649-050-1 (ISBN)
Public defence
2014-12-19, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrheniusväg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 2: Manuscript.

Available from: 2014-11-27 Created: 2014-11-18 Last updated: 2014-11-28Bibliographically approved

Open Access in DiVA

No full text

Search in DiVA

By author/editor
Virkki, Tuuli MinttuPeters, ChristophArne, Elofsson
By organisation
Department of Biochemistry and Biophysics
Biochemistry and Molecular Biology

Search outside of DiVA

GoogleGoogle Scholar

urn-nbn

Altmetric score

urn-nbn
Total: 96 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf