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

TY - JOUR

T1 - Structure formation during translocon-unassisted co-translational membrane protein folding

AU - Harris, Nicola

AU - Reading, Eamonn

AU - Ataka, Kenichi

AU - Grzegorzewski, Lucjan

AU - Charalambous, Kalypso

AU - Liu, Xia

AU - Schlesinger, Ramona

AU - Heberle, Joachim

AU - Booth, Paula

PY - 2017/8/14

Y1 - 2017/8/14

N2 - 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.

AB - 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.

KW - Journal Article

U2 - 10.1038/s41598-017-08522-9

DO - 10.1038/s41598-017-08522-9

M3 - Article

C2 - 28808343

SN - 2045-2322

VL - 7

JO - Scientific Reports

JF - Scientific Reports

IS - 1

ER -