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Structure formation during translocon-unassisted co-translational membrane protein folding

Research output: Contribution to journalArticle

Nicola Harris, Eamonn Reading, Kenichi Ataka, Lucjan Grzegorzewski, Kalypso Charalambous, Xia Liu, Ramona Schlesinger, Joachim Heberle, Paula Booth

Original languageEnglish
Number of pages15
JournalScientific Reports
Volume7
Issue number1
Early online date14 Aug 2017
DOIs
Publication statusPublished - 14 Aug 2017

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Abstract

Correctly folded membrane proteins underlie a plethora of cellular processes, but little is known about how they fold. Knowledge of folding mechanisms centres on reversible folding of chemically denatured membrane proteins. However, this cannot replicate the unidirectional elongation of the protein chain during co-translational folding in the cell, where insertion is assisted by translocase apparatus. We show that a lipid membrane (devoid of translocase components) is sufficient for successful co-translational folding of two bacterial α-helical membrane proteins, DsbB and GlpG. Folding is spontaneous, thermodynamically driven, and the yield depends on lipid composition. Time-resolving structure formation during co-translational folding revealed different secondary and tertiary structure folding pathways for GlpG and DsbB that correlated with membrane interfacial and biological transmembrane amino acid hydrophobicity scales. Attempts to refold DsbB and GlpG from chemically denatured states into lipid membranes resulted in extensive aggregation. Co-translational insertion and folding is thus spontaneous and minimises aggregation whilst maximising correct folding.

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