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[2 forms of influenza virus nucleocapsid protein (NP) in virions and infected cells]
Abstract:
Two forms of the major nucleocapsid protein (NP) of influenza virus were found which an polyacrylamide gel electrophoresis had the mobility corresponding to those of proteins with moleculr weights of 56,000 (NP56) and 53,000 (NP53) daltons. A pulse-chase experiment showed the NP53 polypeptide to be a transformation product of NP56 polypeptide. Peptide mapping indicated that both proteins were quite similar, except that NP56 had two additional peptides suggesting the mechanism of NP53 derivation from NP56 by cleavage of a small peptide (molecular weight about 3000 daltons). Both classes of NP protein molecules were found both in infected cells and in virions. The intensity of intracellular modification NP56 leads to NP53 was dissimilar in different cell lines and practically did not depend on the virus strain. In virus preparations obtained from different cells in NP53 protein content varied but this polypeptide was always found as a minor component. In the infected cells the ratio of NP53 to NP56 polypeptides was significantly higher than in virions indicating the preferable incorporation into the virus progeny of polypeptides with intact NP56 protein.
Insights
Influenza virus nucleocapsid protein (NP) exists in two forms, NP56 and NP53. NP53 is derived from NP56 through peptide cleavage, with NP56 preferentially incorporated into new virus particles.
Area of Science:
- Virology
- Molecular Biology
- Protein Chemistry
Context:
- The influenza virus nucleocapsid protein (NP) is crucial for viral replication and assembly.
- Understanding NP post-translational modifications is key to deciphering viral lifecycle.
- Previous studies identified distinct NP forms, but their relationship and incorporation dynamics were unclear.
Purpose:
- To investigate the relationship between the two identified forms of influenza virus NP (NP56 and NP53).
- To elucidate the mechanism of NP53 formation from NP56.
- To determine the differential incorporation of NP forms into progeny virions.
Summary:
- Two major forms of influenza virus nucleocapsid protein, NP56 and NP53, were identified with distinct molecular weights.
- Pulse-chase experiments revealed NP53 as a transformation product of NP56, likely via cleavage of a 3000-dalton peptide.
- Peptide mapping confirmed structural similarity, with NP56 possessing additional peptides.
- Both NP forms are present in infected cells and virions, but NP56 is preferentially incorporated into progeny viruses.
- The NP56 to NP53 conversion rate varied across cell lines but was independent of the virus strain.
Impact:
- This research clarifies the post-translational modification of influenza virus NP and its implications for viral assembly.
- Identifies NP56 as the preferred form for incorporation into new virions, potentially impacting viral fitness.
- Provides insights into the molecular mechanisms governing influenza virus replication and pathogenesis.