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Isolation and characterization of an extremely basic protein from adenovirus type 5
Abstract:
By starch-gel electrophoresis and a staining method that is highly sensitive for argininyl residues, adenovirus type 5 was found to contain two minor basic polypeptides of extreme cathodic mobility in addition to the two known core proteins. The fastest-migrating polypeptide, named mu protein, and the second fastest polypeptide are found in adenovirions and virus-infected KB cells but not in top components or in uninfected cells. The top components and infected cells contain an additional basic polypeptide, presumably P-VII, that migrates slightly slower than polypeptide VII. None of the basic polypeptides of adenovirions was electrophoretically identical to the host histone. The basic proteins of adenovirions were purified by urea phosphocellulose column chromatography and characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The two minor basic core proteins, mu and another component, have similar mobilities in sodium dodecyl sulfate-polyacrylamide gels as a complex of polypeptides X-XII. After further purification on a Sephadex G-75 column, the mu protein was found to have a molecular weight of about 4,000. Amino acid analysis showed that the mu protein lacks tryptophan and 69% of the total amino acid residues are basic, that is, 54% arginine, 13% histidine, and 2% lysine. Only eight amino acids seem to contribute to make the mu polypeptide. There are 125 copies of the mu polypeptide per 1,000 copies of polypeptide VII in a virion.
Insights
Adenovirus type 5 contains two new minor basic core proteins, including the mu protein. These proteins are essential components of the virus particle and infected cells, distinct from host histones.
Area of Science:
- Virology
- Molecular Biology
- Protein Chemistry
Background:
- Adenovirus type 5 is a well-studied virus with known core proteins.
- Characterization of viral proteins is crucial for understanding viral structure and function.
Purpose of the Study:
- To identify and characterize novel basic polypeptides in adenovirus type 5.
- To investigate the properties and abundance of these newly discovered viral proteins.
Main Methods:
- Starch-gel electrophoresis with sensitive arginine staining.
- Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
- Urea phosphocellulose column chromatography and Sephadex G-75 gel filtration.
- Amino acid analysis.
Main Results:
- Two minor basic polypeptides with high cathodic mobility were identified in adenovirus type 5 virions.
- The fastest migrating polypeptide, named mu protein, was found in virions and infected cells but not in top components or uninfected cells.
- Mu protein has a molecular weight of approximately 4,000, lacks tryptophan, and is composed of 69% basic amino acids (54% arginine, 13% histidine, 2% lysine).
- Mu protein is present at 125 copies per 1,000 copies of polypeptide VII.
Conclusions:
- Adenovirus type 5 possesses previously unidentified minor basic core proteins, including the mu protein.
- These proteins are integral components of the virion and are associated with viral infection.
- The unique amino acid composition and low molecular weight of mu protein suggest specialized functions within the adenovirus structure.