Structural Roles of Polyoma Virus Proteins

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RESUMO

The superhelical, closed circular form of polyoma deoxyribonucleic acid (DNA) (Co 1) is bound in a 25S DNA-protein complex to the viral histone-like proteins after alkaline disruption of the virion. Nicked viral DNA or linear DNA are largely free of protein. Most of the viral protein disruption is in the form of capsomeres, sedimenting principally at 10S and 7S. Despite the relatively constant ratio of 10S to 7S material in many preparations, (1:5.5 to 1:6.0, respectively), the two classes of capsomeres are indistinguishable by electron microscopy and contain only P2, P3, and P4 in molar ratios of approximately 5:1:1 or 6:1:1, respectively. Material with sedimentation rates of approximately 1 to 3S is enriched for P5 and contains small amounts of P2, P3, and P4. During the in vitro reassembly of DNA-free, shell-like particles from disrupted virus, proteins P1, P2, P3, P4, and P7 are reincorporated efficiently, whereas P5 and P6 are not. The presence in empty reassembled particles of histone-like protein, expecially P7, implies that at least this one of the minor protein components of the virion may participate in protein-protein interactions with other components of the capsid.

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