Energetics of side-chain snorkeling in transmembrane helices probed by nonproteinogenic amino acids.
Cotranslational translocon-mediated insertion of membrane proteins into the endoplasmic reticulum is a key process in membrane protein biogenesis. Although the mechanism is understood in outline, quantitative data on the energetics of the process is scarce. Here, we have measured the effect on membrane integration efficiency of nonproteinogenic analogs of the positively charged amino acids arginine and lysine incorporated into model transmembrane segments. We provide estimates of the influence on the apparent free energy of membrane integration (ΔGapp) of "snorkeling" of charged amino acids toward the lipid-water interface, and of charge neutralization. We further determine the effect of fluorine atoms and backbone hydrogen bonds (H-bonds) on ΔGapp These results help establish a quantitative basis for our understanding of membrane protein assembly in eukaryotic cells.
Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden;
Karin
K
Öjemalm
Department of Chemistry, Graduate School of Science, University of Tokyo, 113-0033 Tokyo, Japan;
Takashi
T
Higuchi
Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden;
Patricia
P
Lara
Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-171 21 Solna, Sweden.
Erik
E
Lindahl
Department of Chemistry, Graduate School of Science, University of Tokyo, 113-0033 Tokyo, Japan;
Hiroaki
H
Suga
Department of Biochemistry and Biophysics, Center for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden; Science for Life Laboratory, Stockholm University, SE-171 21 Solna, Sweden gunnar@dbb.su.se.
Gunnar
0000-0002-4490-8569
G
von Heijne
D000596:Amino Acids / Q000737:chemistry* / Q000235:genetics; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*; D019277:Entropy; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D017433:Protein Structure, Secondary; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D000596:Amino Acids; D008051:Lipid Bilayers; D008565:Membrane Proteins; D014867:Water; D012697:Serine Endopeptidases; C026515:type I signal peptidase
membrane protein; nonproteinogenic amino acids; translocon