FEBS Journal

We analyze herein three complementary aspects of the biochemistry of the dynein motor. In the first place the molecular organization and force generating mechanism. Next, the role of dynein light chain DYNLL1 as a dimerization hub is described in detail. Finally, the association of dynein polypeptides with viral proteins and its significance during virus infection is also examined.

Accompanied by a podcast, listen now. Or listen in iTunes

Dynein, which is a minus-end directed microtubule motor, is crucial to a range of cellular processes. This mini-review describes our current knowledge of the molecular organization and the force-generating mechanism of dynein, with emphasis on findings from electron microscopy, X-ray crystallography and single-molecule nanometry.

The highly conserved LC8 dynein light chains interact with a large number of proteins involved in diverse biological functions. Despite earlier suggestion that these chains function as cargo adapters of the dynein motor complex, they are now recognized as regulatory hub proteins that interact with linear motifs located in intrinsically disordered protein segments. The most prominent LC8 function is to promote dimerization of their binding partners.

After fusion with the cellular plasma membrane or endosomal membranes, viral particles are generally too large to diffuse freely within the crowded cytoplasm environment. It has been proposed that many unrelated viruses are transported along microtubules in a retrograde manner using the cellular dynein machinery or, at least, some dynein components, in most cases the light chains DYNLL1, DYNLT1 or DYNLRB1.

The role of a 24 amino-acid C-terminal (CT) extension of a thermostable cysteine protease has been explored. The protease with CT-extension shows a lower activity and autocatalytic zymogen activation at a higher pH. The study reveals that the CT-extension restricts the accessibility of the substrates at the active site and does not have a major role in folding or stability of the enzyme.

Studies of the ion pumps, such as ATP synthetase and Ca²⁺-ATPase, have long histories. Crystal structures of several kinds of ion pumps have been resolved, which provide static pictures of mechanisms of ion transport. In this paper, using fast-scanning atomic force microscopy, we have visualized conformational changes in the sarcoplasmic reticulum Ca²⁺-ATPase (SERCA) in real-time at the single-molecule level.

Here we describe the functions of each domain of a dual-domain BPP from Bacillus sp. HJB17. The incomplete domain was found to hydrolyze phytate intermediate, and to act synergistically with other phytases. Its fusion proteins with other BPPs had significantly enhanced catalytic efficiencies. Thus dual-domain BPPs have succeeded evolutionarily by interacting together to utilize more available phosphate.

The KdpFABC P-type ATPases comprises a novel mode of nucleotide binding, in which the KdpC subunit assists the KdpB nucleotide binding domain in ATP interaction. This catalytic chaperone function involves a sequence signature motif usually found in ABC transporters. ATP binding affinity is strongly increased by the formation of a transient KdpB/KdpC/ATP ternary complex.

The results presented in this study demonstrate that the cellular levels of superoxide anion and nitric oxide were significantly elevated in response to the synthetic immunomodulator muramyl dipeptide (MDP) in macrophages. Mitochondria isolated from cells treated with MDP presented a significant decrease in RCR and up-regulation in the expression of uncoupling protein 2, an effect that was absent following treatment with a non-toxic analogue such as murabutide.

We demonstrate that the germinal center B lymphocyte expressed proteins, HGAL and LMO2, are regulated by the transcription repressor PRDM1. Functional studies, chromatin immunoprecipitation and promoter analysis reveals that PRDM1 directly binds to sites within the promoters of both HGAL and LMO2 and suppresses endogenous protein and mRNA expression. This suggests an important regulatory step in GC B cell differentiation.

In 1 kb promoter region, 953 rice genes contain perfect-, 695 genes gap- and 1584 genes step-type HSE sequences. OsHsfA2c, OsHsfA9 and OsHsfB4b proteins form homotrimers and differentially recognize various model HSEs as a function of varying reaction temperatures. OsHsfB4b shows heteromeric interactions with OsHsfA2a, OsHsfA7, OsHsfB4c and OsHsf26. OsHsfA2c, OsHsfA2d, OsHsfA9, OsHsfC1a and OsHsfC1b show transactivation activity.

Schematic illustration of new approach incorporating a signal amplification circuit to screen transient protein-protein interactions. The G-protein signal induced by the X-Y interaction is amplified by signal-responsive expression of intact Gγ (artificial signal amplifier). As a consequence, the enriched mating response permits practicable selection of the transient X-Y interaction, or GFP expression can be used to estimate the signaling levels.

Extracellular cyclic ADP-ribose (cADPR) enhanced the spontaneous release of adenosine 5′-triphosphate (ATP) in bladder detrusor smooth muscle of CD38^+/+ mice, but not in bladders isolated from CD38^−/− mice. Therefore, cADPR enhanced the release of ATP by influx via CD38 and activation of intracellular cADPR receptors likely causing an increase in intracellular Ca²⁺ in neuronal cells.

Bacterial replicative DNA polymerase PolC has a unique N-terminal region, for which neither the structure nor function is known. Using computational methods we identified in this region two structural domains, both related to domain V of the τ subunit of the clamp loader. We propose that these domains mediate the PolC interaction with the τ subunit and possibly bind DNA.

Apolipoprotein E mediates the catabolism of atherogenic lipoproteins and the de novo biogenesis of HDL, while apoE-deficient mice are resistant to obesity and related metabolic perturbations. Using histological and biochemical methods we report that deficiency in apoE renders mice resistant to diet-induced NAFLD. The data suggest that apoE is key peripheral contributor to hepatic lipid homeostasis and diet-induced NAFLD development.

Plant aminoaldehyde dehydrogenases (AMADHs, EC 1.2.1.19) oxidize polyamine-derived ω-aminoaldehydes to ω-amino acids. The role of the substrate-channel residues in AMADH2 from Pisum sativum was analyzed by site-directed mutagenesis. Carboxylate residues D110 and D113 at the entrance and aromatic residues W288, Y163 and W170 inside the substrate channel determine high affinity and activity of the enzyme with ω-aminoaldehydes.

Initial rate and stopped flow kinetics of zinc inhibition of GDH suggest zinc disrupts subunit interactions required for catalytic competence. Structures with zinc or europium show separate sites at different interfaces and limited proteolysis shows flexibility changes suggesting that this V-type inhibition results from disruption of subunit interactions necessary for efficient catalysis rather than direct effect on the active site.

We investigated the contributions of glutamine and α-ketoglutarate/alanine as substrates for glutamate in glutathione synthesis. When extracellular glutamine or α-ketoglutarate/alanine were at 10 mm, erythrocyte glutathione synthesis was faster with α-ketoglutarate/alanine. Mathematical modelling of glutathione metabolism demonstrated that for erythrocytes in plasma glutamate from both glutamine and α-ketoglutarate/alanine was required to maintain a normal rate of glutathione production.

We cloned the carD gene of Fusarium fujikuroi and investigated the activity of the encoded enzyme. In vivo and in vitro assays, and targeted mutation analysis, demonstrated its function as the aldehyde dehydrogenase producing neurosporaxanthin from its precursor, β-apo-4′-carotenal. With the genetic and biochemical characterization of this enzyme, the whole neurosporaxanthin biosynthetic pathway of this fungus has been established.

The aspartic proteinase gene from one of the seven identified bacterial species, Shewanella amazonensis, was expressed in E. coli. The recombinant protein, termed shewasin A, was shown to display properties remarkably similar to those of pepsin-like aspartic proteinases. It is now beyond doubt that pepsin-like aspartic proteinases are not confined to eukaryotes but are encoded within some species of bacteria.