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Probing Structural Dynamics and Topology of the KCNE1 Membrane Protein in Lipid Bilayers via Site-Directed Spin Labeling and Electron Paramagnetic Resonance Spectroscopy.
Sahu ID, Craig AF, Dunagan MM, Troxel KR, Zhang R, Meiberg AG, Harmon CN, McCarrick RM, Kroncke BM, Sanders CR, Lorigan GA
(2015) Biochemistry 54: 6402-12
MeSH Terms: Amino Acid Sequence, Electron Spin Resonance Spectroscopy, Lipid Bilayers, Molecular Dynamics Simulation, Molecular Sequence Data, Mutagenesis, Site-Directed, Potassium Channels, Voltage-Gated, Protein Conformation
Show Abstract · Added November 21, 2018
KCNE1 is a single transmembrane protein that modulates the function of voltage-gated potassium channels, including KCNQ1. Hereditary mutations in the genes encoding either protein can result in diseases such as congenital deafness, long QT syndrome, ventricular tachyarrhythmia, syncope, and sudden cardiac death. Despite the biological significance of KCNE1, the structure and dynamic properties of its physiologically relevant native membrane-bound state are not fully understood. In this study, the structural dynamics and topology of KCNE1 in bilayered lipid vesicles was investigated using site-directed spin labeling (SDSL) and electron paramagnetic resonance (EPR) spectroscopy. A 53-residue nitroxide EPR scan of the KCNE1 protein sequence including all 27 residues of the transmembrane domain (45-71) and 26 residues of the N- and C-termini of KCNE1 in lipid bilayered vesicles was analyzed in terms of nitroxide side-chain motion. Continuous wave-EPR spectral line shape analysis indicated the nitroxide spin label side-chains located in the KCNE1 TMD are less mobile when compared to the extracellular region of KCNE1. The EPR data also revealed that the C-terminus of KCNE1 is more mobile when compared to the N-terminus. EPR power saturation experiments were performed on 41 sites including 18 residues previously proposed to reside in the transmembrane domain (TMD) and 23 residues of the N- and C-termini to determine the topology of KCNE1 with respect to the 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG) lipid bilayers. The results indicated that the transmembrane domain is indeed buried within the membrane, spanning the width of the lipid bilayer. Power saturation data also revealed that the extracellular region of KCNE1 is solvent-exposed with some of the portions partially or weakly interacting with the membrane surface. These results are consistent with the previously published solution NMR structure of KCNE1 in micelles.
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MeSH Terms
G Protein-Coupled Receptor Kinase 2 (GRK2) and 5 (GRK5) Exhibit Selective Phosphorylation of the Neurotensin Receptor in Vitro.
Inagaki S, Ghirlando R, Vishnivetskiy SA, Homan KT, White JF, Tesmer JJ, Gurevich VV, Grisshammer R
(2015) Biochemistry 54: 4320-9
MeSH Terms: Amino Acid Sequence, Animals, Cattle, G-Protein-Coupled Receptor Kinase 2, G-Protein-Coupled Receptor Kinase 5, Humans, Models, Molecular, Molecular Sequence Data, Phosphorylation, Rats, Receptors, Neurotensin
Show Abstract · Added February 15, 2016
G protein-coupled receptor kinases (GRKs) play an important role in the desensitization of G protein-mediated signaling of G protein-coupled receptors (GPCRs). The level of interest in mapping their phosphorylation sites has increased because recent studies suggest that the differential pattern of receptor phosphorylation has distinct biological consequences. In vitro phosphorylation experiments using well-controlled systems are useful for deciphering the complexity of these physiological reactions and understanding the targeted event. Here, we report on the phosphorylation of the class A GPCR neurotensin receptor 1 (NTSR1) by GRKs under defined experimental conditions afforded by nanodisc technology. Phosphorylation of NTSR1 by GRK2 was agonist-dependent, whereas phosphorylation by GRK5 occurred in an activation-independent manner. In addition, the negatively charged lipids in the immediate vicinity of NTSR1 directly affect phosphorylation by GRKs. Identification of phosphorylation sites in agonist-activated NTSR1 revealed that GRK2 and GRK5 target different residues located on the intracellular receptor elements. GRK2 phosphorylates only the C-terminal Ser residues, whereas GRK5 phosphorylates Ser and Thr residues located in intracellular loop 3 and the C-terminus. Interestingly, phosphorylation assays using a series of NTSR1 mutants show that GRK2 does not require acidic residues upstream of the phospho-acceptors for site-specific phosphorylation, in contrast to the β2-adrenergic and μ-opioid receptors. Differential phosphorylation of GPCRs by GRKs is thought to encode a particular signaling outcome, and our in vitro study revealed NTSR1 differential phosphorylation by GRK2 and GRK5.
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11 MeSH Terms
Notch Transmembrane Domain: Secondary Structure and Topology.
Deatherage CL, Lu Z, Kim JH, Sanders CR
(2015) Biochemistry 54: 3565-8
MeSH Terms: Humans, Lipid Bilayers, Lysophosphatidylcholines, Models, Molecular, Nuclear Magnetic Resonance, Biomolecular, Peptide Fragments, Phosphatidylcholines, Protein Conformation, Protein Structure, Secondary, Protein Structure, Tertiary, Receptor, Notch1, Recombinant Proteins, Surface Properties
Show Abstract · Added February 5, 2016
The Notch signaling pathway is critical in development, neuronal maintenance, and hematopoiesis. An obligate step in the activation of this pathway is cleavage of its transmembrane (TM) domain by γ-secretase. While the soluble domains have been extensively studied, little has been done to characterize its TM and flanking juxtamembrane (JM) segments. Here, we present the results of nuclear magnetic resonance (NMR) studies of the human Notch1 TM/JM domain. The TM domain is largely α-helical. While the flanking JM segments do not adopt regular secondary structure, they interact with the membrane surface, suggesting membrane interactions may play a role in modulating its cleavage by γ-secretase and subsequent NOTCH signaling function.
1 Communities
1 Members
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13 MeSH Terms
Cryo-electron microscopy and the amazing race to atomic resolution.
Binshtein E, Ohi MD
(2015) Biochemistry 54: 3133-41
MeSH Terms: Computer Simulation, Cryoelectron Microscopy, Models, Molecular, Protein Conformation, Proteins
Show Abstract · Added February 4, 2016
Cryo-electron microscopy (cryo-EM), the structural analysis of samples embedded in vitreous ice, is a powerful approach for determining three-dimensional (3D) structures of biological specimens. Over the past two decades, this technique has been used to successfully calculate subnanometer (<10 Å) resolution and, in some cases, near-atomic resolution structures of highly symmetrical and stable complexes such as icosahedral viruses and ribosomes, as well as samples that form ordered two-dimensional or helical arrays. However, determining high-resolution 3D structures of smaller, less symmetrical, and dynamic samples remains a significant challenge. The recent development of electron microscopes with automated data collection capabilities and robust direct electron detection cameras, as well as new powerful image processing algorithms, has dramatically expanded the number of biological macromolecules amenable for study using cryo-EM. In addition, these new technological and computational developments have been used to successfully determine <5 Å resolution 3D structures of samples, such as membrane proteins and complexes with either low or no symmetry, that traditionally were not considered promising candidates for high-resolution cryo-EM. With these exciting new advances, cryo-EM is now on pace to determine atomic resolution 3D structures.
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5 MeSH Terms
Correction to differential stabilities and sequence-dependent base pair opening dynamics of watson-crick base pairs with 5-hydroxymethylcytosine, 5-formylcytosine, or 5-carboxylcytosine.
Szulik MW, Pallan PS, Nocek B, Voehler M, Banerjee S, Brooks S, Joachimiak A, Egli M, Eichman BF, Stone MP
(2015) Biochemistry 54: 2550
Added November 10, 2015
1 Communities
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Personalized biochemistry and biophysics.
Kroncke BM, Vanoye CG, Meiler J, George AL, Sanders CR
(2015) Biochemistry 54: 2551-9
MeSH Terms: Biochemistry, Biophysics, Genetic Linkage, Genetic Predisposition to Disease, Genetic Variation, Genome, Human, Humans, Nucleic Acid Conformation, Precision Medicine, Protein Conformation, RNA
Show Abstract · Added February 5, 2016
Whole human genome sequencing of individuals is becoming rapid and inexpensive, enabling new strategies for using personal genome information to help diagnose, treat, and even prevent human disorders for which genetic variations are causative or are known to be risk factors. Many of the exploding number of newly discovered genetic variations alter the structure, function, dynamics, stability, and/or interactions of specific proteins and RNA molecules. Accordingly, there are a host of opportunities for biochemists and biophysicists to participate in (1) developing tools to allow accurate and sometimes medically actionable assessment of the potential pathogenicity of individual variations and (2) establishing the mechanistic linkage between pathogenic variations and their physiological consequences, providing a rational basis for treatment or preventive care. In this review, we provide an overview of these opportunities and their associated challenges in light of the current status of genomic science and personalized medicine, the latter often termed precision medicine.
1 Communities
3 Members
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11 MeSH Terms
Differential stabilities and sequence-dependent base pair opening dynamics of Watson-Crick base pairs with 5-hydroxymethylcytosine, 5-formylcytosine, or 5-carboxylcytosine.
Szulik MW, Pallan PS, Nocek B, Voehler M, Banerjee S, Brooks S, Joachimiak A, Egli M, Eichman BF, Stone MP
(2015) Biochemistry 54: 1294-305
MeSH Terms: 5-Methylcytosine, Cytosine, DNA, Oligonucleotides, Thymine DNA Glycosylase
Show Abstract · Added April 24, 2015
5-Hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC) form during active demethylation of 5-methylcytosine (5mC) and are implicated in epigenetic regulation of the genome. They are differentially processed by thymine DNA glycosylase (TDG), an enzyme involved in active demethylation of 5mC. Three modified Dickerson-Drew dodecamer (DDD) sequences, amenable to crystallographic and spectroscopic analyses and containing the 5'-CG-3' sequence associated with genomic cytosine methylation, containing 5hmC, 5fC, or 5caC placed site-specifically into the 5'-T(8)X(9)G(10)-3' sequence of the DDD, were compared. The presence of 5caC at the X(9) base increased the stability of the DDD, whereas 5hmC or 5fC did not. Both 5hmC and 5fC increased imino proton exchange rates and calculated rate constants for base pair opening at the neighboring base pair A(5):T(8), whereas 5caC did not. At the oxidized base pair G(4):X(9), 5fC exhibited an increase in the imino proton exchange rate and the calculated kop. In all cases, minimal effects to imino proton exchange rates occurred at the neighboring base pair C(3):G(10). No evidence was observed for imino tautomerization, accompanied by wobble base pairing, for 5hmC, 5fC, or 5caC when positioned at base pair G(4):X(9); each favored Watson-Crick base pairing. However, both 5fC and 5caC exhibited intranucleobase hydrogen bonding between their formyl or carboxyl oxygens, respectively, and the adjacent cytosine N(4) exocyclic amines. The lesion-specific differences observed in the DDD may be implicated in recognition of 5hmC, 5fC, or 5caC in DNA by TDG. However, they do not correlate with differential excision of 5hmC, 5fC, or 5caC by TDG, which may be mediated by differences in transition states of the enzyme-bound complexes.
1 Communities
1 Members
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5 MeSH Terms
Biochemical characterization of a Pseudomonas aeruginosa phospholipase D.
Spencer C, Brown HA
(2015) Biochemistry 54: 1208-18
MeSH Terms: Bacterial Proteins, Cell Line, Humans, Phospholipase D, Pseudomonas aeruginosa, Sequence Homology, Amino Acid, Species Specificity, Substrate Specificity
Show Abstract · Added February 12, 2015
Phospholipase D is a ubiquitous protein in eukaryotes that hydrolyzes phospholipids to generate the signaling lipid phosphatidic acid (PtdOH). PldA, a Pseudomonas aeruginosa PLD, is a secreted protein that targets bacterial and eukaryotic cells. Here we have characterized the in vitro factors that modulate enzymatic activity of PldA, including divalent cations and phosphoinositides. We have identified several similarities between the eukaryotic-like PldA and the human PLD isoforms, as well as several properties in which the enzymes diverge. Notable differences include the substrate preference and transphosphatidylation efficiency for PldA. These findings offer new insights into potential regulatory mechanisms of PldA and its role in pathogenesis.
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8 MeSH Terms
Biochemistry that times the day.
Egli M, Johnson CH
(2015) Biochemistry 54: 104-9
MeSH Terms: Animals, Circadian Clocks, Fungi, Humans, Photoperiod, Plant Development, Seasons
Added February 12, 2015
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7 MeSH Terms
Structural and functional insights into the N-terminus of Schizosaccharomyces pombe Cdc5.
Collier SE, Voehler M, Peng D, Ohi R, Gould KL, Reiter NJ, Ohi MD
(2014) Biochemistry 53: 6439-51
MeSH Terms: Binding Sites, Catalytic Domain, Cell Cycle Proteins, Gene Deletion, Models, Molecular, Mutant Proteins, Nuclear Magnetic Resonance, Biomolecular, Peptide Fragments, Protein Conformation, Protein Folding, Protein Interaction Domains and Motifs, Protein Stability, RNA Splicing, RNA, Double-Stranded, RNA, Fungal, RNA, Small Nuclear, RNA-Binding Proteins, Recombinant Proteins, Schizosaccharomyces pombe Proteins, Spliceosomes, Titrimetry
Show Abstract · Added January 20, 2015
The spliceosome is a dynamic macromolecular machine composed of five small nuclear ribonucleoparticles (snRNPs), the NineTeen Complex (NTC), and other proteins that catalyze the removal of introns mature to form the mature message. The NTC, named after its founding member Saccharomyces cerevisiae Prp19, is a conserved spliceosome subcomplex composed of at least nine proteins. During spliceosome assembly, the transition to an active spliceosome correlates with stable binding of the NTC, although the mechanism of NTC function is not understood. Schizosaccharomyces pombe Cdc5, a core subunit of the NTC, is an essential protein required for pre-mRNA splicing. The highly conserved Cdc5 N-terminus contains two canonical Myb (myeloblastosis) repeats (R1 and R2) and a third domain (D3) that was previously classified as a Myb-like repeat. Although the N-terminus of Cdc5 is required for its function, how R1, R2, and D3 each contribute to functionality is unclear. Using a combination of yeast genetics, structural approaches, and RNA binding assays, we show that R1, R2, and D3 are all required for the function of Cdc5 in cells. We also show that the N-terminus of Cdc5 binds RNA in vitro. Structural and functional analyses of Cdc5-D3 show that, while this domain does not adopt a Myb fold, Cdc5-D3 preferentially binds double-stranded RNA. Our data suggest that the Cdc5 N-terminus interacts with RNA structures proposed to be near the catalytic core of the spliceosome.
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21 MeSH Terms