Solution structure of the region 51–160 of human KIN17 reveals an atypical winged helix domain

Abstract

Human KIN17 is a 45‐kDa eukaryotic DNA‐ and RNA‐binding protein that plays an important role in nuclear metabolism and in particular in the general response to genotoxics. Its amino acids sequence contains a zinc finger motif (residues 28–50) within a 30‐kDa N‐terminal region conserved from yeast to human, and a 15‐kDa C‐terminal tandem of SH3‐like subdomains (residues 268–393) only found in higher eukaryotes. Here we report the solution structure of the region 51–160 of human KIN17. We show that this fragment folds into a three‐α‐helix bundle packed against a three‐stranded β‐sheet. It belongs to the winged helix (WH) family. Structural comparison with analogous WH domains reveals that KIN17 WH module presents an additional and highly conserved 3 10 ‐helix. Moreover, KIN17 WH helix H3 is not positively charged as in classical DNA‐binding WH domains. Thus, human KIN17 region 51–160 might rather be involved in protein–protein interaction through its conserved surface centered on the 3 10 ‐helix.