TY - JOUR
T1 - Understanding the FRET signatures of interacting membrane proteins
AU - King, Christopher
AU - Raicu, Valerica
AU - Hristova, Kalina
N1 - Publisher Copyright:
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc.
PY - 2017/3/31
Y1 - 2017/3/31
N2 - FRET is an indispensable experimental tool for studying membrane proteins. Currently, two models are available for researchers to determine the oligomerization state of membrane proteins in a static quenching FRET experiment: the model of Veatch and Stryer, derived in 1977, and the kinetic theory- based model for intraoligomeric FRET, derived in 2007. Because of confinement in two dimensions, a substantial amount of FRET is generated by energy transfer between fluorophores located in separate oligomers in the two-dimensional bilayer. This interoligomeric FRET (also known as stochastic, bystander, or proximity FRET) is not accounted for in either model. Here, we use the kinetic theory formalism to describe the dependence of the FRET efficiency measured in an experiment (i.e. the "total apparentFRETefficiency") on the interoligomeric FRET due to random proximity within the bilayer and the intraoligomeric FRET resulting from protein-protein interactions. We find that data analysis with both models without consideration of the proximity FRET leads to incorrect conclusions about the oligomeric state of the protein. We show that knowledge of the total surface densities of fluorophore-labeled membrane proteins is essential for correctly interpreting the measured total apparent FRET efficiency. We also find that bulk, two-color, static quenching FRET experiments are best suited for the study of monomeric, dimerizing, or dimeric proteins but have limitations in discerning the order of larger oligomers. The theory and methodology described in this work will allow researchers to extract meaningful parameters from static quenching FRET measurements in biological membranes.
AB - FRET is an indispensable experimental tool for studying membrane proteins. Currently, two models are available for researchers to determine the oligomerization state of membrane proteins in a static quenching FRET experiment: the model of Veatch and Stryer, derived in 1977, and the kinetic theory- based model for intraoligomeric FRET, derived in 2007. Because of confinement in two dimensions, a substantial amount of FRET is generated by energy transfer between fluorophores located in separate oligomers in the two-dimensional bilayer. This interoligomeric FRET (also known as stochastic, bystander, or proximity FRET) is not accounted for in either model. Here, we use the kinetic theory formalism to describe the dependence of the FRET efficiency measured in an experiment (i.e. the "total apparentFRETefficiency") on the interoligomeric FRET due to random proximity within the bilayer and the intraoligomeric FRET resulting from protein-protein interactions. We find that data analysis with both models without consideration of the proximity FRET leads to incorrect conclusions about the oligomeric state of the protein. We show that knowledge of the total surface densities of fluorophore-labeled membrane proteins is essential for correctly interpreting the measured total apparent FRET efficiency. We also find that bulk, two-color, static quenching FRET experiments are best suited for the study of monomeric, dimerizing, or dimeric proteins but have limitations in discerning the order of larger oligomers. The theory and methodology described in this work will allow researchers to extract meaningful parameters from static quenching FRET measurements in biological membranes.
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U2 - 10.1074/jbc.M116.764282
DO - 10.1074/jbc.M116.764282
M3 - Article
C2 - 28188294
AN - SCOPUS:85016582609
SN - 0021-9258
VL - 292
SP - 5291
EP - 5310
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 13
ER -