we suggest that phosphoprotein ' a ' is a high energy protein intermediate in which the phosphate is present as a phosphoramidate for the following reasons : ( i ) guanosine diphosphate ( gdp ) but not guanosine 5'-o- ( 2-thiodiphosphate ) selectively accelerated the dephosphorylation of phosphoprotein ' a ' but only in the presence of mg2+ ions .
C0033684
protein
C0031689
phosphoprotein