ADP-Ribosylation of Brain Neuronal Proteins Is Altered by In Vitro and In Vivo Exposure to Inorganic Mercury

Abstract: ADP-ribosylation is an essential process in the metabolism of brain neuronal proteins, including the regulation of assembly and disassembly of biological polymers. Here, we examine the effect of HgCl₂ exposure on the ADP-ribosylation of tubulin and actin, both cytoskeletal proteins also found in neurons, and B-50/43-kDa growth-associated protein (B-50/GAP-43), a neuronal tissue-specific phosphoprotein. In rats we demonstrate, with both in vitro and in vivo experiments, that HgCl₂ markedly inhibits the ADP-ribosylation of tubulin and actin. This is direct quantitative evidence that HgCl₂, a toxic xenobiotic, alters specific neurochemical reactions involved in maintaining brain neuron structure.     

The Ontogeny of Vocal Sequences: Insights from a Newborn Wild Chimpanzee (Pan troglodytes schweinfurthii)

International Journal of Primatology - Observations of early vocal behaviours in non-human primates (hereafter primates) are important for direct comparisons between human and primate vocal...     

Domain movements of elongation factor eEF2 and the eukaryotic 80S ribosome facilitate tRNA translocation

An 11.7-A-resolution cryo-EM map of the yeast 80S.eEF2 complex in the presence of the antibiotic sordarin was interpreted in molecular terms, revealing large conformational changes within eEF2 and the 80S ribosome, including a rearrangement of the functionally important ribosomal intersubunit bridges. Sordarin positions domain III of eEF2 so that it can interact with the sarcin-ricin loop of 25S rRNA and protein rpS23 (S12p). This particular conformation explains the inhibitory action of sordarin and suggests that eEF2 is stalled on the 80S ribosome in a conformation that has similarities with the GTPase activation state. A ratchet-like subunit rearrangement (RSR) occurs in the 80S.eEF2.sordarin complex that, in contrast to Escherichia coli 70S ribosomes, is also present in vacant 80S ribosomes. A model is suggested, according to which the RSR is part of a mechanism for moving the tRNAs during the translocation reaction.     

The Hemagglutinin of Bat-Associated Influenza Viruses Is Activated by TMPRSS2 for pH-Dependent Entry into Bat but Not Human Cells

New World bats have recently been discovered to harbor influenza A virus (FLUAV)-related viruses, termed bat-associated influenza A-like viruses (batFLUAV). The internal proteins of batFLUAV are functional in mammalian cells. In contrast, no biological functionality could be demonstrated for the surface proteins, hemagglutinin (HA)-like (HAL) and neuraminidase (NA)-like (NAL), and these proteins need to be replaced by their human counterparts to allow spread of batFLUAV in human cells. Here, we employed rhabdoviral vectors to study the role of HAL and NAL in viral entry. Vectors pseudotyped with batFLUAV-HAL and -NAL were able to enter bat cells but not cells from other mammalian species. Host cell entry was mediated by HAL and was dependent on prior proteolytic activation of HAL and endosomal low pH. In contrast, sialic acids were dispensable for HAL-driven entry. Finally, the type II transmembrane serine protease TMPRSS2 was able to activate HAL for cell entry indicating that batFLUAV can utilize human proteases for HAL activation. Collectively, these results identify viral and cellular factors governing host cell entry driven by batFLUAV surface proteins. They suggest that the absence of a functional receptor precludes entry of batFLUAV into human cells while other prerequisites for entry, HAL activation and protonation, are met in target cells of human origin.     

MOFOID--not only the protein modeling server

MOFOID is a new server developed mainly for automated modeling of protein structures by their homology to the structures deposited in the PDB database. Selection of a template and calculation of the alignment is performed with the Smith-Waterman or Needleman-Wunsch algorithms implemented in the EMBOSS package. The final model is built and optimised with programs from the JACKAL package. The wide spectrum of options in the web-based interface and the possibility of uploading user's own alignment make MOFOID a suitable platform for testing new approaches in the alignment building. The server is available at https:// valis.ibb.waw.pl/mofoid/.     

Munc18a controls SNARE assembly through its interaction with the syntaxin N-peptide

Sec1/Munc18-like (SM) proteins functionally interact with SNARE proteins in vesicular fusion. Despite their high sequence conservation, structurally disparate binding modes for SM proteins with syntaxins have been observed. Several SM proteins appear to bind only to a short peptide present at the N terminus of syntaxin, designated the N-peptide, while Munc18a binds to a 'closed' conformation formed by the remaining portion of syntaxin 1a. Here, we show that the syntaxin 16 N-peptide binds to the SM protein Vps45, but the remainder of syntaxin 16 strongly enhances the affinity of the interaction. Likewise, the N-peptide of syntaxin 1a serves as a second binding site in the Munc18a/syntaxin 1a complex. When the syntaxin 1a N-peptide is bound to Munc18a, SNARE complex formation is blocked. Removal of the N-peptide enables binding of syntaxin 1a to its partner SNARE SNAP-25, while still bound to Munc18a. This suggests that Munc18a controls the accessibility of syntaxin 1a to its partners, a role that might be common to all SM proteins.     

Backbone dynamics of green fluorescent protein and the effect of histidine 148 substitution

Green fluorescent protein (GFP) and its mutants have become valuable tools in molecular biology. GFP has been regarded as a very stable and rigid protein with the beta-barrel shielding the chromophore from the solvent. Here, we report the 15N nuclear magnetic resonance (NMR) studies on the green fluorescent protein (GFPuv) and its mutant His148Gly. 15N NMR relaxation studies of GFPuv show that most of the beta-barrel of GFP is rigid on the picosecond to nanosecond time scale. For several regions, including the first alpha-helix and beta-sheets 3, 7, 8, and 10, increased hydrogen-deuterium exchange rates suggest a substantial conformational flexibility on the microsecond to millisecond time scales. Mutation of residue 148 located in beta-sheet 7 is known to have a strong impact on the fluorescence properties of GFPs. UV absorption and fluorescence spectra in combination with 1H-15N NMR spectra indicate that the His148Gly mutation not only reduces the absorption of the anionic chromophore state but also affects the conformational stability, leading to the appearance of doubled backbone amide resonances for a number of residues. This suggests the presence of two conformations in slow exchange on the NMR time scale in this mutant.