MAJOR VAULT PROTEIN OF ELECTRIC RAY IS A PHOSPHOPROTEIN

The major vault protein is the predominant member of a large cytosolic ribonucleoprotein particle, named vaults. Vaults are abundant in nerv e terminals of the electric organ of Torpedo marmorata. Negative stain ing of isolated vaults reveals particle dimensions of 45 X 65 nm in si ze. Comparison of the major vault protein (MVP100) from the two electr ic ray species Torpedo marmorata and Discopyge ommata reveals few micr oheterogeneities in amino acid sequence. Potential phosphorylation sit es for various protein kinases are highly conserved. Phosphorylation s tudies demonstrate that the major vault protein of Torpedo is a substr ate of various protein kinases. MVP100 is phosphorylated by protein ty rosine kinase in vivo and protein kinase C and casein kinase II in vit ro. Inhibitors and activators of protein kinases specifically modulate the phosphorylation of MVP100.