Direction of elongation of poly(ADP-ribose) chains. Addition of residues at the polymerase-proximal terminus.

摘要: Abstract The mechanism of elongation poly(ADP-ribose) on polymerase was examined in two ways. first technique involved a pulse-chase protocol. Poly(ADP-ribose) labeled with radioactive NAD, excess precursor removed by rapid gel filtration chromatography, and nonradioactive NAD supplied for second incubation. products were released alkali digested venom phosphodiesterase which generates AMP uniquely from the distal terminus. residue that during pulse remained at terminus not converted to an internal chase. employed analog, 2'-deoxyNAD (dNAD), can engage mono-ADP-ribose addition reactions but lacks 2'-OH is required polymer formation. dNAD inhibits ADP-ribose incorporation competitively incorporated enzyme-distal chain These findings are inconsistent model synthesis new residues added growing chain, attachment. They consistent alternative possibility 1" terminus, adjacent polymerase. Any such "proximal addition" requires there be least active center sites (akin ribosomal A P sites), certain stage each cycle will occupied monomers polymers, respectively. Although does enter poly(ADP-ribose), it slow side reaction whereby single dADP-ribose covalently itself, thereby inactivating enzyme.