This is the N-terminal domain of poly ADP-ribose polymerase (PARP16 also known as ARTD15) present in homo sapiens. ARTDs catalyse the formation of branched or unbranched chains of ADP-ribose units on protein side chains. The N-terminal domain of ARTD15 does not share any obvious sequence similarity with the regulatory domains of ARTD1-4. The N-terminal domain arrangement in both ARTD15 and ARTD1-3 suggests a regulatory role through different mechanisms [1].

1: Crystal structure of human ADP-ribose transferase ARTD15/PARP16 reveals a novel putative regulatory domain. Karlberg T, Thorsell AG, Kallas A, Schuler H; J Biol Chem. 2012;287:24077-24081. PMID:22661712