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Abstract

The Parvovirus B19, known to cause disease in humans, has been shown to produce two small, unique, nonstructural proteins of 7.5 and 11 kilodaltons (kDa). No functional significance, nor homology with other proteins, has yet been attributed to either the 7.5 kDa or the 11 kDa B19 proteins. However, due to the small coding capacity of B19 it is thought that these two proteins most likely play a functional role in the replication cycle of this virus. Due to its narrow host range no continuous cell line permissive for B19 infection is available for routine investigation. Therefore, studies must be performed in the absence of a permissive cell line. Previous studies have failed to demonstrate Zn++ binding or transactivation activities for either protein. Neither have been shown to be phosphorylated, nor to interact with other known viral proteins. However, the 7.5 kDa protein has been implicated in interactions with proteins within a lysate of COS-7 cells. Therefore, further investigations have focused on interactions of both the 7.5 kDa and 11 kDa B19 proteins with host cellular proteins. Far western blot experiments indicate that two COS-7 cellular proteins of 43 kDa and 55 kDa, in addition to lower molecular weight proteins, may interact with the 7.5 kDa B19 protein. Western blot experiments suggests that the 55 kDa cellular protein is most likely vimentin. Results of affinity column experiments utilizing glutathione S-transferase fusion proteins suggest that the 11 kDa protein may interact with two K-562 cellular proteins of approximately 27 kDa and 85 kDa. These interactions were substantiated with further batch affinity experiments. In addition, preliminary far western studies demonstrate an in vitro interaction between Growth Factor Receptor Binding protein-2 (Grb2) and the 11 kDa B19 protein. This suggests that the 11 kDa protein may enable B19 to influence its host cell environment. [Scientific formulae used in this abstract could not be reproduced.]