VapC-like PIN domain of rRNA-processing protein, Fcf1 (Utp24, YDR339C), and other eukaryotic homologs.
Fcf1/Utp24 (FAF1-copurifying factor 1/U three-associated protein 24) is an essential protein involved in pre-rRNA processing and 40S ribosomal subunit assembly. Component of the small subunit (SSU) processome, Fcf1 is an essential nucleolar protein that is required for processing of the 18S pre-rRNA at sites A0-A2. The Fcf1 protein was reported to interact with Pmc1p (vacuolar Ca2+ ATPase) and Cor1p (core subunit of the ubiquinol-cytochrome c reductase complex). The PIN (PilT N terminus) domain belongs to a large nuclease superfamily. The structural properties of the PIN domain indicate its active center, consisting of three highly conserved catalytic residues which coordinate metal ions; in some members, additional metal coordinating residues can be found while some others lack several of these key catalytic residues. Most members of the Fcf1 PIN domain subfamily have four of these conserved residues and the Fcf1-Utp23 homolog PIN domain subfamily has three. Point mutation studies of the conserved acidic residues in the putative active site of Saccharomyces cerevisiae Fcf1 determined they were essential for pre-rRNA processing at sites A1 and A2, whereas the presence of the Fcf1 protein itself is also required for cleavage at site A0.
Comment:Point mutation studies showed that conserved catalytic residues in the putative active site of Saccharomyces cerevisiae Fcf1 are essential for 18S pre-rRNA processing at sites A1 and A2, most members of the Fcf1 PIN domain subfamily have four of these conserved residues and the Fcf1-Utp23 homology PIN domain subfamily has three.
Jiyao W et al.(2023). "The conserved domain database in 2023.",