An unexpected effect of divalent cations on the adenovirus endogenous protein kinase: alteration in the specificity...

Area of Science:

• Virology
• Molecular Biology
• Biochemistry

Background:

• Adenovirus protein kinase is an endogenous viral enzyme.
• This kinase phosphorylates viral capsid proteins, a crucial step in viral replication.
• Magnesium ions (Mg2+) are typically required for kinase activity.

Purpose of the Study:

• To investigate the effect of substituting magnesium ions with manganese (Mn2+) or cobalt (Co2+) on adenovirus protein kinase activity.
• To determine if these substitutions alter the substrate specificity or phosphorylation profile of the kinase.

Main Methods:

• In vitro kinase assays using adenovirus endogenous protein kinase.
• Phosphorylation of viral capsid protein IIIa, and core proteins V and VII.
• Substitution of Mg2+ with Mn2+ or Co2+ in the presence of ATP or GTP.
• Analysis of phosphoamino acid residues (phosphoserine, phosphothreonine).

Main Results:

• Mn2+ or Co2+ enhanced phosphorylation of capsid protein IIIa by 2-3 fold compared to Mg2+.
• In the presence of Mn2+ or Co2+, core proteins V and VII, typically not phosphorylated, became targets.
• Phosphorylation shifted from exclusively phosphoserine to include significant phosphothreonine labeling when Mn2+ or Co2+ were used.

Conclusions:

• Mn2+ and Co2+ ions interact differently with adenovirus structural proteins compared to Mg2+.
• These interactions likely increase the accessibility of viral proteins to the endogenous kinase.
• The altered ion-binding facilitates broader substrate phosphorylation and changes the phosphoamino acid profile.