Human immunodeficiency virus (HIV)Vpr contributes to nuclear import of the viral pre-integration complex and induces G 2 cell cycle arrest. We describe the production of synthetic Vpr that permitted the first studies on the structure and folding of the full-length protein. Vpr is unstructured at neutral pH, whereas under acidic conditions or upon addition of trifluorethanol it adopts ␣-helical structures. Vpr forms dimers in aqueous trifluorethanol, whereas oligomers exist in pure water.1 H NMR spectroscopy allows the signal assignment of N-and C-terminal amino acid residues; however, the central section of the molecule is obscured by self-association. These findings suggest that the in vivo folding of Vpr may require structure-stabilizing interacting factors such as previously described interacting cellular and viral proteins or nucleic acids. In biological studies we found that Vpr is efficiently taken up from the extracellular medium by cells in a process that occurs independent of other HIV-1 proteins and appears to be independent of cellular receptors. Following cellular uptake, Vpr is efficiently imported into the nucleus of transduced cells. Extracellular addition of Vpr induces G 2 cell cycle arrest in dividing cells. Together, these findings raise the possibility that circulating forms of Vpr observed in HIV-infected patients may exert biological effects on a broad range of host target cells.
Recently, a novel 87-amino acid influenza A virus protein with proapoptotic properties, PB1-F2, has been reported that originates from an alternative reading frame in the PB1 polymerase gene and is encoded in most known human influenza A virus isolates. Here we characterize the molecular structure of a biologically active synthetic version of the protein (sPB1-F2). Western blot analysis, chemical cross-linking, and NMR spectroscopy afforded direct evidence of the inherent tendency of sPB1-F2 to undergo oligomerization mediated by two distinct domains located in the N and C termini, respectively. CD and 1 H NMR spectroscopic analyses indicate that the stability of structured regions in the molecule clearly depends upon the hydrophobicity of the solvent. In aqueous solutions, the behavior of sPB1-F2 is typical of a largely random coil peptide that, however, adopts ␣-helical structure upon the addition of membrane mimetics.1 H NMR analysis of three overlapping peptides afforded, for the first time, direct experimental evidence of the presence of a C-terminal region with strong ␣-helical propensity comprising amino acid residues Ile 55 -Lys 85 connected via an essentially random coil structure to a much weaker helix-like region, located in the N terminus between residues Trp 9 and Lys 20 . The C-terminal helix is not a true amphipathic helix and is more compact than previously predicted. It corresponds to a positively charged region previously shown to include the mitochondrial targeting sequence of PB1-F2. The consequences of the strong oligomerization and helical propensities of the molecule are discussed and used to formulate a hypothetical model of its interaction with the mitochondrial membrane.Influenza A virus (IAV) 3 is one of the most common pathogens threatening humans and animals, with the potential to cause disastrous pandemics. In the last century, it was the origin of at least three pandemics, the most serious outbreak being the "Spanish flu" (1918 -1919) that claimed 20 -50 million casualties worldwide (for a review, see Ref. 1). Apart from various mammals, IAV also infects avian hosts, and particularly aquatic birds have been shown to be the primary reservoir. Sporadically, some of these avian strains acquire the capability to infect other mammals or humans either as a whole or more likely upon genetic reassortment with prevailing human IAV strains. This process termed antigenic (viral) shift appears to occur via the pig as an intermediate host and "mixing vessel" and can lead to new IAV subtypes of mixed surface antigens (2, 3).The genome of IAV, a representative of the orthomyxoviruses, consists of eight separate linear segments of negative sense RNA and was thought to encode 10 gene products. Only very recently, while screening for major histocompatibility complex class I epitopes derived from out-of-frame viral polypeptides, an 11th IAV gene product, named PB1-F2, was incidentally discovered (4). Like the two proteins M1 (matrix protein) and M2 (ion channel) encoded on the M gene segment and t...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.