Semliki forest virus core protein fragmentation: Its possible role in nucleocapsid disassembly |
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Authors: | Andreas Schlegel Johann Schaller Pia Jentsch Christoph Kempf |
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Institution: | (1) Central Laboratory, Blood Transfusion Service, Swiss Red Cross, Wankdorfstrasse 10, 3000 Bern 22, Switzerland;(2) Institute of Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland;(3) Present address: Department of Molecular, Cellular and Developmental Biology, University of Colorado at Boulder, 80309-0347 Boulder, Colorado, USA |
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Abstract: | Semliki Forest virus (SFV) envelope proteins function as proton pores under mildly acidic conditions and translocate protons across the viral membrane Schlegel, A., Omar, A., Jentsch, P., Morell, A. and Kemp, F. C. (1991) Biosci. Rep. 11, 243–255]. As a consequence, during uptake of SFV by cells via receptor-mediated endocytosis the nucleocapsid is supposed to be exposed to protons. In this paper the effects of mildly acidic pH on SFV nucleocapsids were examined. A partial proteolytic fragmentation of core proteins was observed when nucleocapsids were exposed to mildly acidic pH. A similar proteolytic event was detected when intact SFV virions were exposed to identical conditions. Protease protection assays with exogenous bromelain provided evidence that the capsid protein degradation was due to an endogenous proteolytic activity and not to a proteolytic contamination. Detergent solubilization of virus particles containing degraded nucleocapsids followed by sucrose gradient centrifugation led to a separation of capsid protein fragments and remaining nucleocapsids. These data are discussed in terms of a putative biological significance, namely that the core protein fragmentation may play a role in nucleocapsid disassembly. |
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Keywords: | Semliki Forest virus (SFV) virus entry nucleocapsid disassembly capsid protein |
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