NOPS domain, including C-terminal coiled-coil region, in p54nrb/PSF/PSP1 homologs from invertebrate species
The family contains a DBHS domain (for Drosophila behavior, human splicing), which comprises two conserved RNA recognition motifs (RRMs), also termed RBDs (RNA binding domains) or RNPs (ribonucleoprotein domains), and a charged protein-protein interaction NOPS (NONA and PSP1) domain. This model corresponds to the NOPS domain, with a long helical C-terminal extension , found in Drosophila melanogaster gene no-ontransient A (nonA) encoding puff-specific protein Bj6 (also termed NONA), Chironomus tentans hrp65 gene encoding protein Hrp65 and similar proteins. D. melanogaster NONA is involved in eye development and behavior, and may play a role in circadian rhythm maintenance, similar to vertebrate p54nrb. C. tentans hrp65 is a component of nuclear fibers associated with ribonucleoprotein particles in transit from the gene to the nuclear pore. The NOPS domain specifically binds to the second RNA recognition motif (RRM2) domain of the partner DBHS protein via a substantial interaction surface. Its highly conserved C-terminal residues are critical for functional DBHS dimerization while the highly conserved C-terminal helical extension, forming a right-handed antiparallel heterodimeric coiled-coil, is essential for localization of these proteins to subnuclear bodies.
Jiyao W et al.(2023). "The conserved domain database in 2023.",