VERTEBRATE MONO-ADP-RIBOSYLTRANSFERASES

Mono-ADP-ribosylation appears to be a reversible modification of prote ins, which occurs in many eukaryotic and prokaryotic organisms. Multip le forms of arginine-specific ADP-ribosyltransferases have been purifi ed and characterized from avian erythrocytes, chicken polymorphonuclea r leukocytes and mammalian skeletal muscle. The avian transferases hav e similar molecular weights of similar to 28 kDa, but differ in physic al, regulatory and kinetic properties and subcellular localization. Re cently, a 38-kDa rabbit skeletal muscle ADP-ribosyltransferase was pur ified and cloned. The deduced amino acid sequence contained hydrophobi c amino and carboxy termini, consistent with known signal sequences of glycosylphosphatidylinositol (GPI)-anchored proteins. This arginine-s pecific transferase was present on the surface of mouse myotubes and o f NMU cells transfected with the cDNA and was released with phosphatid ylinositol-specific phospholipase C. Arginine-specific ADP-ribosyltran sferases thus appear to exhibit considerable diversity in their struct ure, cellular localization, regulation and physiological role.