Mechanistic insights revealed by the crystal structure of a histidine kinase with signal transducer and sensor domains.

Two-component systems (TCSs) are important for the adaptation and survival of bacteria and fungi under stress conditions. A TCS is often composed of a membrane-bound sensor histidine kinase (SK) and a response regulator (RR), which are relayed through sequential phosphorylation steps. However, the mechanism for how an SK is switched on in response to environmental stimuli remains obscure. Here, we report the crystal structure of a complete cytoplasmic portion of an SK, VicK from Streptococcus mutans. The overall structure of VicK is a long-rod dimer that anchors four connected domains: HAMP, Per-ARNT-SIM (PAS), DHp, and catalytic and ATP binding domain (CA). The HAMP, a signal transducer, and the PAS domain, major sensor, adopt canonical folds with dyad symmetry. In contrast, the dimer of the DHp and CA domains is asymmetric because of different helical bends in the DHp domain and spatial positions of the CA domains. Moreover, a conserved proline, which is adjacent to the phosphoryl acceptor histidine, contributes to helical bending, which is essential for the autokinase and phosphatase activities. Together, the elegant architecture of VicK with a signal transducer and sensor domain suggests a model where DHp helical bending and a CA swing movement are likely coordinated for autokinase activation.

Complete mitochondrial genome of the copepod Sinergasilus undulates (Copepoda: Poecilostomatoida).

The total mitochondrial genome size of Sinergasilus undulatus is 14,239 bp in length, including 13 protein-coding genes (PCGs), two rRNA genes, 22 transfer RNA genes, and a non-coding control region (D-loop). The overall nucleotide composition of the mitochondrial DNA of S. undulatus is 34.9% A, 35.5% T, 15.7% C, 13.9% G, and 70.4% AT, respectively. Phylogenetic analysis suggests that the genus Sinergasilus is monophyletic, and S. undulatus is closely related to S. polycolpus. The complete mitochondrial genome of S. undulatus would be useful for species identification, epidemiology, and phylogenetics among Copepods.

Neuroprotective effects of pretreatment with propofol in LPS-induced BV-2 microglia cells: role of TLR4 and GSK-3ß.

Surgery often leads to neuroinflammation, which mainly acts as the activation of microglia cells. Propofol is always used for induction and maintenance of anesthesia prior to surgical trauma, whereas whether or not it could attenuate neuroinflammation used prophylactically is not well defined. In the present study, we incubated BV-2 microglia cells with 1 µg/ml lipopolysaccharide (LPS) to mimic neuroinflammation in vitro. Firstly, cell viability was measured using 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay and the data indicated that propofol would not reduce cell viability unless its concentration reached 300 µM. Secondly, BV-2 microglia cells were pretreated with 30 µM propofol (clinically relevant concentration), and then stimulated with LPS. The results showed that the production of tumor necrosis factor-α (TNF-α), interleukin (IL)-1ß and IL-10 was considerably increased by LPS, but the change could be markedly attenuated by pretreatment with propofol. Meanwhile, pretreatment with propofol inhibited LPS-induced augmentation of toll-like receptor 4 (TLR4) expression at both mRNA and protein levels and further upregulated LPS-induced inactivation of glycogen synthase kinase-3ß (GSK-3ß) in BV-2 microglia cells. These results indicated, at least in part, that pretreatment with propofol can protect BV-2 microglia cells against LPS-induced inflammation. Downregulation of TLR4 expression and inactivation of GSK-3ß may be involved in its protective effect.