Adenosine diphosphate ribulose in human erythrocytes: a new metabolite with membrane binding properties

Incubation of ADPribose with yeast phosphoriboisomerase resulted in the formation of an adenylic nucleotide that was identified with ADPribulose by mass spectrometry. Synthesis of [32P]ADPribulose from [32P]NAD+ by the combined activities of commercial NAD+ glycohydrolase and phosphoriboisomerase allowed us to use it as a labeled internal standard throughout the procedure of purification from trichloroacetic acid extracts of human red blood cells. ADPribulose was purified by means of three sequential reverse phase HPLC separations and its concentration in human erythrocytes was estimated to be 0.11 +/- 0.1 microM. Unsealed erythrocyte ghosts did not transform ADPribulose, which bound to specific membrane proteins with a trichloroacetic and formic acid-resistant binding. The labeled proteins were identified as spectrin, bands 3, 4.1, 4.2 and Glyceraldehyde 3-phosphate dehydrogenase on the basis of their relative mobilities on SDS-PAGE.