| Summary: | 碩士 === 國立中興大學 === 生物化學研究所 === 90 === Bamboo mosaic potexvirus (BaMV), which primarily infects members of the Bambusoideae, has a single-stranded positive-sense RNA genome that composes five major open reading frames (ORFs). Proteins encoded by ORFs 2, 3 and 4 of BaMV share similar features with the products of the corresponding ‘triple-gene-block’ (TGB) of other potexviruses. All of them are required for the cell-to-cell movement of viral RNA. With the aid of immunogold labeling and electron microscopy, it has been demonstrated that TGBp1 is associated with electron dense crystalline bodies (EDCBs) observed in cytoplasm, nuclei and nucleoli of infected leaf tissues, with coat protein (CP) and virus particle being detected in the neighbourhood of EDCBs. It has been also reported that the soluble form of TGBp1 possesses nonspecific RNA-binding activity at an ionic strength (50 mM NaCl) much lower than that expected for plant cells. Recently, it was reported that the viral RNA, TGBp1 and CP form ribonucleoprotein complex, which is able to move from cell to cell in the plant tissues. On the basis of the above-mentioned fact, it was assumed that there are certain factors, which are able to assist the binding of TGBp1 to viral RNA under physiological condition. And CP may be one of the factors. To prove this idea, the TGBP1 and CP proteins were first overproduced and purified. After denaturation and refolding, the soluble forms of these two proteins (TGBp1 and CP) were assayed for their RNA-binding activity through the use of a UV-cross linking technique. The present data revealed that TGBp1 or CP was able to bind RNA by itself at both pH8.0 and 7.4. Moreover, both TGBp1 and CP were able to enhance the RNA-binding activity of each other at certain molar ratios of protein to viral RNA.
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