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Structural investigation of the transmembrane domain of KCNE1 in proteoliposomes.

Sahu ID, Kroncke BM, Zhang R, Dunagan MM, Smith HJ, Craig A, McCarrick RM, Sanders CR, Lorigan GA - Biochemistry (2014)

Bottom Line: Experimentally derived DEER distances coupled with simulated annealing molecular dynamic simulations were used to probe the bilayer structure of the TMD of KCNE1.The results indicate that the structure is helical in proteoliposomes and is slightly curved, which is consistent with the previously determined solution NMR structure in micelles.The evident resilience of the curvature in the KCNE1 TMD leads us to hypothesize that the curvature is likely to be maintained upon binding of the protein to the KCNQ1 channel.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States.

ABSTRACT
KCNE1 is a single-transmembrane protein of the KCNE family that modulates the function of voltage-gated potassium channels, including KCNQ1. Hereditary mutations in KCNE1 have been linked to diseases such as long QT syndrome (LQTS), atrial fibrillation, sudden infant death syndrome, and deafness. The transmembrane domain (TMD) of KCNE1 plays a key role in mediating the physical association with KCNQ1 and in subsequent modulation of channel gating kinetics and conductance. However, the mechanisms associated with these roles for the TMD remain poorly understood, highlighting a need for experimental structural studies. A previous solution NMR study of KCNE1 in LMPG micelles revealed a curved transmembrane domain, a structural feature proposed to be critical to KCNE1 function. However, this curvature potentially reflects an artifact of working in detergent micelles. Double electron electron resonance (DEER) measurements were conducted on KCNE1 in LMPG micelles, POPC/POPG proteoliposomes, and POPC/POPG lipodisq nanoparticles to directly compare the structure of the TMD in a variety of different membrane environments. Experimentally derived DEER distances coupled with simulated annealing molecular dynamic simulations were used to probe the bilayer structure of the TMD of KCNE1. The results indicate that the structure is helical in proteoliposomes and is slightly curved, which is consistent with the previously determined solution NMR structure in micelles. The evident resilience of the curvature in the KCNE1 TMD leads us to hypothesize that the curvature is likely to be maintained upon binding of the protein to the KCNQ1 channel.

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Schematic model of the overlay of the10 lowest energy structures of KCNE1 TMD in a lipid bilayer.
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fig7: Schematic model of the overlay of the10 lowest energy structures of KCNE1 TMD in a lipid bilayer.

Mentions: The newly determined structureswere further validated with the BSL-based experimental DEER distances.The back-calculated distances between dual-BSLs attached on the newlydetermined lowest energy structure are consistent with the experimentalBSL distances within experimental error of ±2 Å (Table S2). The DEER determined structures andthe previously determined solution NMR structure in micelles are overlaidin Figure 6C. The backbone RMSDs for all ofthe superimposed new structures with respect to the previous NMR structurevary between 1.5 to 3.0 Å (see Table S3). The residue positions on the concave face of the KCNE1 TMD inthe new structure model are comparable to those of the previouslydetermined NMR structure. Additional details for the output structuresare given in the Supporting Information. These new structures indicate that the KCNE1 TMD adopts a similar,slightly curved conformation when compared to the previously publishedsolution NMR structure in LMPG micelles.1 The predicted structural model of KCNE1 in a lipid bilayer is givenin Figure 7.


Structural investigation of the transmembrane domain of KCNE1 in proteoliposomes.

Sahu ID, Kroncke BM, Zhang R, Dunagan MM, Smith HJ, Craig A, McCarrick RM, Sanders CR, Lorigan GA - Biochemistry (2014)

Schematic model of the overlay of the10 lowest energy structures of KCNE1 TMD in a lipid bilayer.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4196734&req=5

fig7: Schematic model of the overlay of the10 lowest energy structures of KCNE1 TMD in a lipid bilayer.
Mentions: The newly determined structureswere further validated with the BSL-based experimental DEER distances.The back-calculated distances between dual-BSLs attached on the newlydetermined lowest energy structure are consistent with the experimentalBSL distances within experimental error of ±2 Å (Table S2). The DEER determined structures andthe previously determined solution NMR structure in micelles are overlaidin Figure 6C. The backbone RMSDs for all ofthe superimposed new structures with respect to the previous NMR structurevary between 1.5 to 3.0 Å (see Table S3). The residue positions on the concave face of the KCNE1 TMD inthe new structure model are comparable to those of the previouslydetermined NMR structure. Additional details for the output structuresare given in the Supporting Information. These new structures indicate that the KCNE1 TMD adopts a similar,slightly curved conformation when compared to the previously publishedsolution NMR structure in LMPG micelles.1 The predicted structural model of KCNE1 in a lipid bilayer is givenin Figure 7.

Bottom Line: Experimentally derived DEER distances coupled with simulated annealing molecular dynamic simulations were used to probe the bilayer structure of the TMD of KCNE1.The results indicate that the structure is helical in proteoliposomes and is slightly curved, which is consistent with the previously determined solution NMR structure in micelles.The evident resilience of the curvature in the KCNE1 TMD leads us to hypothesize that the curvature is likely to be maintained upon binding of the protein to the KCNQ1 channel.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry and Biochemistry, Miami University , Oxford, Ohio 45056, United States.

ABSTRACT
KCNE1 is a single-transmembrane protein of the KCNE family that modulates the function of voltage-gated potassium channels, including KCNQ1. Hereditary mutations in KCNE1 have been linked to diseases such as long QT syndrome (LQTS), atrial fibrillation, sudden infant death syndrome, and deafness. The transmembrane domain (TMD) of KCNE1 plays a key role in mediating the physical association with KCNQ1 and in subsequent modulation of channel gating kinetics and conductance. However, the mechanisms associated with these roles for the TMD remain poorly understood, highlighting a need for experimental structural studies. A previous solution NMR study of KCNE1 in LMPG micelles revealed a curved transmembrane domain, a structural feature proposed to be critical to KCNE1 function. However, this curvature potentially reflects an artifact of working in detergent micelles. Double electron electron resonance (DEER) measurements were conducted on KCNE1 in LMPG micelles, POPC/POPG proteoliposomes, and POPC/POPG lipodisq nanoparticles to directly compare the structure of the TMD in a variety of different membrane environments. Experimentally derived DEER distances coupled with simulated annealing molecular dynamic simulations were used to probe the bilayer structure of the TMD of KCNE1. The results indicate that the structure is helical in proteoliposomes and is slightly curved, which is consistent with the previously determined solution NMR structure in micelles. The evident resilience of the curvature in the KCNE1 TMD leads us to hypothesize that the curvature is likely to be maintained upon binding of the protein to the KCNQ1 channel.

Show MeSH
Related in: MedlinePlus