InterPro domain: IPR037503

Fcf1 (also known as Utp24) is an essential protein involved in pre-rRNA processing and 40S ribosomal subunit assembly [ 1 ]. As a component of the small subunit (SSU) processome, Fcf1 is an essential nucleolar protein required for processing of the 18S pre-rRNA at sites A0-A2 [ 2 ].

The PIN (PilT N terminus) domain is a compact RNA-binding protein domain found in all domains of life. Typically, the PIN domain contains three or four conserved acidic residues (putative metal-binding, active site residues) [ 3 ]. The Fcf1 PIN domain has four of these putative active site residues and the Fcf1-Utp23 homologue PIN domain has three of them. 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 [ 4 , 4 ].

1. Fcf1p and Fcf2p are novel nucleolar Saccharomyces cerevisiae proteins involved in pre-rRNA processing. Biochem. Biophys. Res. Commun. 346, 546-54
2. The PINc domain protein Utp24, a putative nuclease, is required for the early cleavage steps in 18S rRNA maturation. Proc. Natl. Acad. Sci. U.S.A. 103, 9464-9
3. Structural conservation of the PIN domain active site across all domains of life. Protein Sci. 26, 1474-1492