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Publication Abstract from PubMed

ScARP from the bacterium Streptomyces coelicolor belongs to the pierisin family of DNA-targeting ADP-ribosyltransferases (ARTs). These enzymes ADP-ribosylate the N(2) amino groups of guanine residues in DNA to yield N(2)-(ADP-ribos-1-yl)-2'-deoxyguanosine. Although the structures of pierisin-1 and Scabin were revealed recently, the substrate recognition mechanisms remain poorly understood because of the lack of a substrate-binding structure. Here, we report the apo structure of ScARP and of ScARP bound to NADH and its GDP substrate at 1.50 and 1.57 A resolutions, respectively. The bound structure revealed that the guanine of GDP is trapped between N-ribose of NADH and Trp159. Interestingly, N(2) and N(3) of guanine formed hydrogen bonds with the OE1 and NE2 atoms of Gln162, respectively. We directly observed that the ADP-ribosylating toxin turn-turn (ARTT)-loop including Trp159 and Gln162 plays a key role in the specificity of DNA-targeting guanine-specific ART as well as protein-targeting ARTs such as C3 exoenzyme. We propose that the ARTT-loop recognition is a common substrate recognition mechanism in the pierisin family. Furthermore, this complex structure sheds light on similarities and differences among two subclasses that are distinguished by conserved structural motifs: H-Y-E in the ARTD subfamily and R-S-E in the ARTC subfamily. The spatial arrangements of the electrophile and nucleophile were the same, providing the first evidence for a common reaction mechanism in these ARTs. ARTC (including ScARP) uses the ARTT-loop for substrate recognition, whereas ARTD (represented by Arr) uses the C-terminal helix instead of the ARTT-loop. These observations could help inform efforts to improve ART inhibitors.

Substrate N(2) atom recognition mechanism in pierisin family DNA-targeting guanine-specific ADP-ribosyltransferase ScARP.,Yoshida T, Tsuge H J Biol Chem. 2018 Aug 2. pii: AC118.004412. doi: 10.1074/jbc.AC118.004412. PMID:30072382^[3]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.