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Energetics of side-chain partitioning of β-signal residues in unassisted folding of a transmembrane β-barrel protein.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2017 Jul 21; Vol. 292 (29), pp. 12351-12365. Date of Electronic Publication: 2017 Jun 07. - Publication Year :
- 2017
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Abstract
- The free energy of water-to-interface amino acid partitioning is a major contributing factor in membrane protein folding and stability. The interface residues at the C terminus of transmembrane β-barrels form the β-signal motif required for assisted β-barrel assembly in vivo but are believed to be less important for β-barrel assembly in vitro Here, we experimentally measured the thermodynamic contribution of all 20 amino acids at the β-signal motif to the unassisted folding of the model β-barrel protein PagP. We obtained the partitioning free energy for all 20 amino acids at the lipid-facing interface (ΔΔ G <superscript>0</superscript> <subscript>w,i</subscript> <subscript>(φ)</subscript> ) and the protein-facing interface (ΔΔ G <superscript>0</superscript> <subscript>w,i</subscript> <subscript>(π)</subscript> ) residues and found that hydrophobic amino acids are most favorably transferred to the lipid-facing interface, whereas charged and polar groups display the highest partitioning energy. Furthermore, the change in non-polar surface area correlated directly with the partitioning free energy for the lipid-facing residue and inversely with the protein-facing residue. We also demonstrate that the interface residues of the β-signal motif are vital for in vitro barrel assembly, because they exhibit a side chain-specific energetic contribution determined by the change in nonpolar accessible surface. We further establish that folding cooperativity and hydrophobic collapse are balanced at the membrane interface for optimal stability of the PagP β-barrel scaffold. We conclude that the PagP C-terminal β-signal motif influences the folding cooperativity and stability of the folded β-barrel and that the thermodynamic contributions of the lipid- and protein-facing residues in the transmembrane protein β-signal motif depend on the nature of the amino acid side chain.<br /> (© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.)
- Subjects :
- Acyltransferases metabolism
Amino Acid Motifs
Energy Transfer
Enzyme Stability
Escherichia coli Proteins metabolism
Gene Deletion
Hydrophobic and Hydrophilic Interactions
Micelles
Molecular Dynamics Simulation
Phosphatidylcholines chemistry
Phosphorylcholine analogs & derivatives
Phosphorylcholine chemistry
Protein Conformation, beta-Strand
Protein Folding
Protein Interaction Domains and Motifs
Protein Structure, Secondary
Surface Properties
Thermodynamics
Acyltransferases chemistry
Amino Acids chemistry
Escherichia coli K12 enzymology
Escherichia coli Proteins chemistry
Lipid Bilayers chemistry
Models, Molecular
Subjects
Details
- Language :
- English
- ISSN :
- 1083-351X
- Volume :
- 292
- Issue :
- 29
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 28592485
- Full Text :
- https://doi.org/10.1074/jbc.M117.789446