title: Properties of African Cassava Mosaic Virus Capsid Protein Expressed in Fission Yeast.
abstract: The capsid proteins (CPs) of geminiviruses combine multiple functions for packaging the single-stranded viral genome, insect transmission and shuttling between the nucleus and the cytoplasm. African cassava mosaic virus (ACMV) CP was expressed in fission yeast, and purified by SDS gel electrophoresis. After tryptic digestion of this protein, mass spectrometry covered 85% of the amino acid sequence and detected three N-terminal phosphorylation sites (threonine 12, serines 25 and 62). Differential centrifugation of cell extracts separated the CP into two fractions, the supernatant and pellet. Upon isopycnic centrifugation of the supernatant, most of the CP accumulated at densities typical for free proteins, whereas the CP in the pellet fraction showed a partial binding to nucleic acids. Size-exclusion chromatography of the supernatant CP indicated high order complexes. In DNA binding assays, supernatant CP accelerated the migration of ssDNA in agarose gels, which is a first hint for particle formation. Correspondingly, CP shifted ssDNA to the expected densities of virus particles upon isopycnic centrifugation. Nevertheless, electron microscopy did not reveal any twin particles, which are characteristic for geminiviruses.
authors.affiliation: Department of Molecular Biology and Plant Virology, Institute of Biomaterials and Biomolecular Systems, University of Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany. katharina.hipp@bio.uni-stuttgart.de.
authors.forename: Katharina
authors.initials: K
authors.lastname: Hipp
authors.affiliation: Department of Molecular Biology and Plant Virology, Institute of Biomaterials and Biomolecular Systems, University of Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany. benjamin.schaefer@bio.uni-stuttgart.de.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Schäfer
authors.affiliation: Department of Molecular Biology and Plant Virology, Institute of Biomaterials and Biomolecular Systems, University of Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany. gabi.kepp@bio.uni-stuttgart.de.
authors.forename: Gabi
authors.initials: G
authors.lastname: Kepp
authors.affiliation: Department of Molecular Biology and Plant Virology, Institute of Biomaterials and Biomolecular Systems, University of Stuttgart, Pfaffenwaldring 57, D-70550 Stuttgart, Germany. holger.jeske@bio.uni-stuttgart.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Jeske
mesh_terms: D053839:Begomovirus / Q000235:genetics*; D036022:Capsid Proteins / Q000235:genetics / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D004279:DNA, Viral; D015870:Gene Expression; D011485:Protein Binding; D055503:Protein Multimerization; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*
chemical_list: D036022:Capsid Proteins; D004279:DNA, Viral; D011994:Recombinant Proteins
keywords: CP; DNA binding assay; capsid protein; ectopic expression; fission yeast; geminivirus