Background Paper Functions of the Coronavirus Nucleocapsid Protein
In 1962 Caspar and Klug conjectured that self-assembly of equivalent or quasi-equivalent protein subunits and viral nucleic acid produces either icosahedral or helical structures according to the biological functions required (1). Some 15 years later Wengler introduced the terms “transcription helices” and “translation helices” to describe the relationship between helical ribonucleoprotein (RNP) structure and genome function for animal viruses containing single-stranded RNA (2). In transcription helices the RNA genome is transcribed into complementary nucleic acid, without permanent disassembly of the RNP. In translation helices the RNA is liberated from the RNP and translated into protein. To account for the fact that no examples of enveloped viruses containing translation helices had been described, Wengler speculated that “the forces exerted on the viral RNP during budding necessitate the design of a helical RNP of such high stability that RNA cannot be released for translation in vivo. Therefore, translation helices will not be present in viruses which obtain a viral membrane by budding”.
KeywordsNucleocapsid Protein Mouse Hepatitis Virus Human Coronavirus Virus Nucleocapsid Protein Complementary Nucleic Acid
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