The C2 Domain and Altered ATP-Binding Loop Phosphorylation at Ser³⁵⁹ Mediate the Redox-Dependent Increase in Protein Kinase C-δ Activity.

The diverse roles of protein kinase C-δ (PKCδ) in cellular growth, survival, and injury have been attributed to stimulus-specific differences in PKCδ signaling responses. PKCδ exerts membrane-delimited actions in cells activated by agonists that stimulate phosphoinositide hydrolysis. PKCδ is released from membranes as a Tyr(313)-phosphorylated enzyme that displays a high level of lipid-independent activity and altered substrate specificity during oxidative stress.

Positions of the cytoplasmic end of BK α S0 helix relative to S1-S6 and of β1 TM1 and TM2 relative to S0-S6.

The large-conductance, voltage- and Ca(2+)-gated K(+) (BK) channel consists of four α subunits, which form a voltage- and Ca(2+)-gated channel, and up to four modulatory β subunits. The β1 subunit is expressed in smooth muscle, where it slows BK channel kinetics and shifts the conductance-voltage (G-V) curve to the left at [Ca(2+)] > 2 µM. In addition to the six transmembrane (TM) helices, S1-S6, conserved in all voltage-dependent K(+) channels, BK α has a unique seventh TM helix, S0, which may contribute to the unusual rightward shift in the G-V curve of BK α in the absence of β1 and to a leftward shift in its presence.

Conformational analysis of NMDA receptor GluN1, GluN2, and GluN3 ligand-binding domains reveals subtype-specific characteristics.

The NMDA receptor family of glutamate receptor ion channels is formed by obligate heteromeric assemblies of GluN1, GluN2, and GluN3 subunits. GluN1 and GluN3 bind glycine, whereas GluN2 binds glutamate. Crystal structures of the GluN1 and GluN3A ligand-binding domains (LBDs) in their apo states unexpectedly reveal open- and closed-cleft conformations, respectively, with water molecules filling the binding pockets.

Location of modulatory beta subunits in BK potassium channels.

Large-conductance voltage- and calcium-activated potassium (BK) channels contain four pore-forming alpha subunits and four modulatory beta subunits. From the extents of disulfide cross-linking in channels on the cell surface between cysteine (Cys) substituted for residues in the first turns in the membrane of the S0 transmembrane (TM) helix, unique to BK alpha, and of the voltage-sensing domain TM helices S1-S4, we infer that S0 is next to S3 and S4, but not to S1 and S2. Furthermore, of the two beta1 TM helices, TM2 is next to S0, and TM1 is next to TM2.

Location of the beta 4 transmembrane helices in the BK potassium channel.

Large-conductance, voltage- and Ca(2+)-gated potassium (BK) channels control excitability in a number of cell types. BK channels are composed of alpha subunits, which contain the voltage-sensor domains and the Ca(2+)- sensor domains and form the pore, and often one of four types of beta subunits, which modulate the channel in a cell-specific manner. beta 4 is expressed in neurons throughout the brain.

Molecular mechanism of ligand recognition by NR3 subtype glutamate receptors.

NR3 subtype glutamate receptors have a unique developmental expression profile, but are the least well-characterized members of the NMDA receptor gene family, which have key roles in synaptic plasticity and brain development. Using ligand binding assays, crystallographic analysis, and all atom MD simulations, we investigate mechanisms underlying the binding by NR3A and NR3B of glycine and D-serine, which are candidate neurotransmitters for NMDA receptors containing NR3 subunits. The ligand binding domains of both NR3 subunits adopt a similar extent of domain closure as found in the corresponding NR1 complexes, but have a unique loop 1 structure distinct from that in all other glutamate receptor ion channels.

Characterization of a soluble ligand binding domain of the NMDA receptor regulatory subunit NR3A.

NR3A is expressed widely in the developing CNS of mammals. Coassembly of NR3A with NR1 and NR2 modifies NMDA receptor-mediated responses, reducing calcium permeability and single-channel conductance. The ligand binding properties of NR3A are unknown but shape the role NR3A plays when incorporated into NMDA receptors.

The C-terminal appended domain of human cytosolic leucyl-tRNA synthetase is indispensable in its interaction with arginyl-tRNA synthetase in the multi-tRNA synthetase complex.

Human cytosolic leucyl-tRNA synthetase is one component of a macromolecular aminoacyl-tRNA synthetase complex. This is unlike prokaryotic and lower eukaryotic LeuRSs that exist as free soluble enzymes. There is little known about it, since the purified enzyme has been unavailable.

A T-stem slip in human mitochondrial tRNALeu(CUN) governs its charging capacity.

The human mitochondrial tRNALeu(CUN) [hmtRNALeu(CUN)] corresponds to the most abundant codon for leucine in human mitochondrial protein genes. Here, in vitro studies reveal that the U48C substitution in hmtRNALeu(CUN), which corresponds to the pathological T12311C gene mutation, improved the aminoacylation efficiency of hmtRNALeu(CUN). Enzymatic probing suggested a more flexible secondary structure in the wild-type hmtRNALeu(CUN) transcript compared with the U48C mutant.

Reduction of mitochondrial tRNALeu(UUR) aminoacylation by some MELAS-associated mutations.

The mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes syndrome (MELAS) is a rare congenital disorder of mitochondrial DNA. Five single nucleotide substitutions within the human mitochondrial tRNALeu(UUR) gene have been reported to be associated with MELAS. Here, we provide in vitro evidence that the aminoacylation capacities of these five hmtRNALeu(UUR) transcripts are reduced to different extents relative to the wild-type hmtRNALeu(UUR) transcript.

Escherichia coli tRNA(4)(Arg)(UCU) induces a constrained conformation of the crucial Omega-loop of arginyl-tRNA synthetase.

Previous investigations show that tRNA(Arg)-induced conformational changes of arginyl-tRNA synthetase (ArgRS) Omega-loop region (Escherichia coli (E. coli), Ala451-Ala457) may contribute to the productive conformation of the enzyme catalytic core, and E. coli tRNA(2)(Arg)(ICG)-bound and -free conformations of the Omega-loop exchange at an intermediate rate on NMR timescale.

Arginyl-tRNA synthetase with signature sequence KMSK from Bacillus stearothermophilus.

ArgRS (arginyl-tRNA synthetase) belongs to the class I aaRSs (aminoacyl-tRNA synthetases), though the majority of ArgRS species lack the canonical KMSK sequence characteristic of class I aaRSs. A DNA fragment of the ArgRS gene from Bacillus stearothermophilus was amplified using primers designed according to the conserved regions of known ArgRSs. Through analysis of the amplified DNA sequence and known tRNA(Arg)s with a published genomic sequence of B.

Substrate-induced conformational changes in Escherichia coli arginyl-tRNA synthetase observed by 19F NMR spectroscopy.

The 19F nuclear magnetic resonance (NMR) spectra of 4-fluorotryptophan (4-F-Trp)-labeled Escherichia coli arginyl-tRNA synthetase (ArgRS) show that there are distinct conformational changes in the catalytic core and tRNA anticodon stem and loop-binding domain of the enzyme, when arginine and tRNA(Arg) are added to the unliganded enzyme. We have assigned five fluorine resonances of 4-F-Trp residues (162, 172, 228, 349 and 446) in the spectrum of the fluorinated enzyme by site-directed mutagenesis. The local conformational changes of E.

Human mitochondrial leucyl-tRNA synthetase with high activity produced from Escherichia coli.

The processing of human mitochondrial leucyl-tRNA synthetase had been previously investigated in insect cell. In the present work, the gene encoding human mitochondrial leucyl-tRNA synthetase with the same N-terminus as that processed in the mitochondria of insect cell was cloned and expressed in Escherichia coli. The enzyme was purified by affinity chromatography on Ni-NTA column.