Merck
  • Home
  • Search Results
  • Differential backbone dynamics of companion helices in the extended helical coiled-coil domain of a bacterial chemoreceptor.

Differential backbone dynamics of companion helices in the extended helical coiled-coil domain of a bacterial chemoreceptor.

Protein science : a publication of the Protein Society (2015-08-11)
Nicholas L Bartelli, Gerald L Hazelbauer
ABSTRACT

Cytoplasmic domains of transmembrane bacterial chemoreceptors are largely extended four-helix coiled coils. Previous observations suggested the domain was structurally dynamic. We probed directly backbone dynamics of this domain of the transmembrane chemoreceptor Tar from Escherichia coli using site-directed spin labeling and electron paramagnetic resonance (EPR) spectroscopy. Spin labels were positioned on solvent-exposed helical faces because EPR spectra for such positions reflect primarily polypeptide backbone movements. We acquired spectra for spin-labeled, intact receptor homodimers solubilized in detergent or inserted into native E. coli lipid bilayers in Nanodiscs, characterizing 16 positions distributed throughout the cytoplasmic domain and on both helices of its helical hairpins, one amino terminal to the membrane-distal tight turn (N-helix), and the other carboxyl terminal (C-helix). Detergent solubilization increased backbone dynamics for much of the domain, suggesting that loss of receptor activities upon solubilization reflects wide-spread destabilization. For receptors in either condition, we observed an unanticipated difference between the N- and C-helices. For bilayer-inserted receptors, EPR spectra from sites in the membrane-distal protein-interaction region and throughout the C-helix were typical of well-structured helices. In contrast, for approximately two-thirds of the N-helix, from its origin as the AS-2 helix of the membrane-proximal HAMP domain to the beginning of the membrane-distal protein-interaction region, spectra had a significantly mobile component, estimated by spectral deconvolution to average approximately 15%. Differential helical dynamics suggests a four-helix bundle organization with a pair of core scaffold helices and two more dynamic partner helices. This newly observed feature of chemoreceptor structure could be involved in receptor function.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Glycerin, meets USP testing specifications
Sigma-Aldrich
Sodium chloride solution, 5 M
Sigma-Aldrich
Sodium chloride solution, 5 M in H2O, BioReagent, for molecular biology, suitable for cell culture
Sigma-Aldrich
Sodium chloride solution, 0.9% in water, BioXtra, suitable for cell culture
Sigma-Aldrich
Sodium chloride, meets analytical specification of Ph. Eur., BP, USP, 99.0-100.5%
Sigma-Aldrich
Sodium chloride, for molecular biology, DNase, RNase, and protease, none detected, ≥99% (titration)
Sigma-Aldrich
Sodium chloride, BioReagent, suitable for cell culture, suitable for insect cell culture, suitable for plant cell culture, ≥99%
Sigma-Aldrich
Sodium chloride, tablet
Sigma-Aldrich
Sodium chloride, BioXtra, ≥99.5% (AT)
Sigma-Aldrich
Sodium chloride, AnhydroBeads, −10 mesh, 99.99% trace metals basis
Sigma-Aldrich
Sodium chloride, AnhydroBeads, −10 mesh, 99.999% trace metals basis
Sigma-Aldrich
Sodium chloride, BioUltra, for molecular biology, ≥99.5% (AT)
Sigma-Aldrich
Sodium chloride solution, 0.85%
Sigma-Aldrich
Sodium chloride, 99.999% trace metals basis
Sigma-Aldrich
Glycerol solution, 83.5-89.5% (T)
Sigma-Aldrich
Sodium chloride solution, BioUltra, for molecular biology, ~5 M in H2O
Sigma-Aldrich
Phenylmethanesulfonyl fluoride, ≥99.0% (T)
Sigma-Aldrich
Sodium chloride-35Cl, 99 atom % 35Cl
Sigma-Aldrich
Sodium chloride, random crystals, optical grade, 99.9% trace metals basis
Sigma-Aldrich
Phenylmethanesulfonyl fluoride, ≥98.5% (GC)
Sigma-Aldrich
Sodium chloride, Vetec, reagent grade, 99%
Sigma-Aldrich
Glycerol solution, puriss., meets analytical specification of Ph. Eur., BP, 84-88%
Sigma-Aldrich
Glycerol solution, puriss. p.a., 86-89% (T)
SAFC
Sodium chloride solution, 5 M
Sigma-Aldrich
Sodium chloride, BioPerformance Certified, ≥99% (titration), suitable for insect cell culture, suitable for plant cell culture
Sigma-Aldrich
Glycerol, puriss., meets analytical specification of Ph. Eur., BP, USP, FCC, E422, anhydrous, 99.0-101.0% (alkalimetric)
Sigma-Aldrich
Ethylenediaminetetraacetic acid, anhydrous, crystalline, BioReagent, suitable for cell culture
Sigma-Aldrich
Ethylenediaminetetraacetic acid, purified grade, ≥98.5%, powder
Sigma-Aldrich
Ethylenediaminetetraacetic acid, ACS reagent, 99.4-100.6%, powder
Sigma-Aldrich
Ethylenediaminetetraacetic acid, BioUltra, anhydrous, ≥99% (titration)