Binding of retrovirus-associated protein kinase and proteins to Staphylococcus aureus

Area of Science:

• Virology
• Biochemistry
• Microbiology

Background:

• Staphylococcus aureus, particularly strain Cowan, is used to isolate antigen-antibody complexes.
• Protein A on S. aureus mediates binding, but other strains lacking it also bind viral components.
• Murine leukemia viruses (MuLV) are retroviruses known to carry various proteins, including kinases.

Purpose of the Study:

• To investigate the binding of protein kinase activity from Moloney murine leukemia virus (Mo-MuLV) to Staphylococcus aureus.
• To identify viral proteins that bind to S. aureus and characterize their interaction with kinase activity.
• To explore the binding of cellular kinase activity to S. aureus from virus-infected cells.

Main Methods:

• Formalin-fixed Staphylococcus aureus (strains Cowan and Wood) used for binding experiments.
• Assay of protein kinase activity via [gamma-32P]ATP phosphorylation of casein.
• Elution of bound proteins and kinase activity using varying salt concentrations (0.5 M KCl).
• Analysis of [3H]leucine-labeled viral proteins by gel electrophoresis.
• Gel filtration chromatography to separate eluted components.

Main Results:

• Both protein A-positive and protein A-negative S. aureus strains bound kinase activity from disrupted Mo-MuLV.
• Approximately 50% of bound kinase activity was eluted by 0.5 M KCl.
• S. aureus also bound casein kinase activity from uninfected and R-MuLV- or Mo-MuLV-infected cell extracts.
• Two major viral proteins, p15 and p10, selectively bound to S. aureus.
• Viral p10 and bound kinase activity co-eluted, separating into a complex and a monomeric p10 form upon gel filtration.

Conclusions:

• Staphylococcus aureus can bind protein kinase activity associated with Moloney murine leukemia virus.
• Viral proteins p10 and p15 are involved in the binding to S. aureus.
• The p10 protein appears to be associated with the bound kinase activity, forming a complex that can be separated from monomeric p10.