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Alternative expression of a chitosanase gene produces two different proteins in cells infected with Chlorella virus
T Yamada1, S Hiramatsu, P Songsri
1Department of Fermentation Technology, Faculty of Engineering, Hiroshima University, Japan. tayamad@ipc.hiroshimau.ac.jp
Abstract:
Several Chlorella virus CVK2 proteins had chitosanase and/or chitinase activities. A gene coding for an ORF of 328 amino acids (aa) with a predicted molecular mass of 36,769 Da was cloned from the viral genome. The predicted amino acid sequence of an N'-portion (174 aa) of this gene product (vChta-1) showed 22 to 25% identity with various bacterial chitosanases. A glutathione S-transferase (GST)-vChta-1 fusion protein had strong chitosanase activity. Western blot analysis with antisera raised against the vChta-1 protein identified two proteins of 37 and 65 kDa in virus-infected Chlorella cells beginning at 240 min postinfection and continuing until cell lysis. The larger protein was packaged in the virion, while the smaller one remained in the cell lysate. Both chitosanase proteins were produced from the single gene, vChta-1, by a mechanism of alternative gene expression.