Mitochondrial Ribosomal Protein S4 (MRPS4)

IMP3 forms a ternary complex with IMP4 and MPP10 (MPHOSPHO10) that interacts with U3 small nucleolar RNA (snoRNA), which is required for the early cleavage steps in pre-rRNA processing .

The deduced 180-amino acid protein has a calculated molecular mass of 21.8 kD and shares approximately 50% identity with yeast Imp3. IMP3 contains a predicted coiled-coil domain and an S4 domain. Fluorescence microscopy localized IMP3 to the nucleoli in transfected Hep2 cells.Glycerol gradient cosedimentation and GST pull-down studies showed that IMP3, IMP4, and MPP10 form a heterotrimeric protein complex. Analysis of deletion mutants showed that both the IMP3 S4 domain and coiled-coil region are required for interaction with MPP10 amino acids 457 to 565.