Amino acid substitutions affecting aspartic acid 605 and valine 606 decrease the interaction strength between the influenza virus RNA polymerase PB2 '627' domain and the viral nucleoprotein.

The influenza virus RNA genome is transcribed and replicated in the context of the viral ribonucleoprotein (vRNP) complex by the viral RNA polymerase. The nucleoprotein (NP) is the structural component of the vRNP providing a scaffold for the viral RNA. In the vRNP as well as during transcription and replication the viral polymerase interacts with NP but it is unclear which parts of the polymerase and NP mediate these interactions. Previously the C-terminal '627' domain (amino acids 538-693) of PB2 was shown to interact with NP. Here we report that a fragment encompassing amino acids 146-185 of NP is sufficient to mediate this interaction. Using NMR chemical shift perturbation assays we show that amino acid region 601 to 607 of the PB2 '627' domain interacts with this fragment of NP. Substitutions of these PB2 amino acids resulted in diminished RNP activity and surface plasmon resonance assays showed that amino acids D605 was essential for the interaction with NP and V606 may also play a partial role in the interaction. Collectively these results reveal a possible interaction surface between NP and the PB2 subunit of the RNA polymerase complex.

Structural characterization and immuno-modulating activities of a polysaccharide from Ganoderma sinense.

A protein-bound polysaccharide (GSP-4) with a molecular weight of 8.3 × 105 Da, was isolated from the water extract of the fruiting bodies of Ganoderma sinense. Chemical study revealed that this fraction was composed of mannose, glucose and galactose in the molar ratio of 4.7:27.1:1.0, with the sugar residues of t-, 1,3-, 1,4-, 1,6-, 1,3,4- and 1,3,6-linked Glcp, t-linked Galp, and 1,6-linked Manp. The immnomodulatory effects of GSP-4 were assessed using human peripheral blood mononuclear cells (PBMCs) and murine monocyte/macrophage cell line RAW 264.7. We found that GSP-4 could significantly stimulate the production of the immunomodulatory markers tumor necrosis factor α (TNF-α), interleukin (IL)-1ß, IL-12, and granulocyte-macrophage colony-stimulating factor (GM-CSF) in PBMCs. This observation was further substantiated in RAW 264.7 cells, as indicated by the increase of nitric oxide (NO), TNF-α and IL-6 production. GSP-4 also enhanced the expression of inducible NO synthase mRNA in dose-dependent manner. Our current finding gives the first piece of evidence to support that GSP-4 possesses some promising immunomodulating effects and it could be a potential candidate to be further used in related cancer immunotherapy.

Isolation, structure characterization, and immunomodulating activity of a hyperbranched polysaccharide from the fruiting bodies of Ganoderma sinense.

A polysaccharide (GSP-6B) with a molecular mass of 1.86 × 106 Da was isolated from the fruiting bodies of Ganoderma sinense . Chemical composition analysis, methylation analysis, infrared spectroscopy, and nuclear magnetic resonance spectroscopy were conducted to elucidate its structure. GSP-6B contains a backbone of (1→6)-linked-ß-D-glucopyranosyl residues, bearing branches at the O-3 position of every two sugar residues along the backbone. The side chains contain (1→4)-linked-ß-D-glucopyranosyl residues, (1→3)-linked-ß-D-glucopyranosyl residues, and nonreducing end ß-D-glucopyranosyl residues. An in vitro immunomodulating activity assay revealed that GSP-6B could significantly induce the release of IL-1ß and TNF-α in human peripheral blood mononuclear cell (PBMC) and showed no toxicity to either PBMC or a human macrophage cell line THP-1. GSP-6B could also activate dendritic cells (DC) by stimulating the secretion of IL-12 and IL-10 from DC.