Rpf2 is a conserved protein essential for the maturation of 25 S rRNA and the 60 S ribosomal subunit assembly []. It is part of the complex (Rpf2/Rrs1/rpL5/rpL11) that functions in intermediate stages of 66S preribosome maturation and assembles into 90S preribosomes containing 35S pre-rRNA [].
This family consists of BRX1 and homologues. In yeast, BRX1 is part of a complex that also includes RPF1, RPF2 and SSF1 or SSF2. It is required for biogenesis of the 60S ribosomal subunit [].
This domain normally occurs as tandem repeats. It is found in resuscitation-promoting factors RpfB from Mycobacterium tuberculosis and Rpf2 from Corynebacterium glutamicum. These are factors that stimulate resuscitation of dormant cells [].
Analysis of the Brix (biogenesis of ribosomes in Xenopus) protein leaded to the identification of a region of 150-180 residues length, called the Brixdomain, which is found in six protein families: one archaean family (I) including hypothetical proteins (one per genome); and five eukaryote families, each named according to a representative member and including close homologues of this prototype: (II) Peter Pan (D. melanogaster) and SSF1/2 (S.cerevisiae); (III) RPF1 (S. cerevisiae); (IV) IMP4 (S. cerevisiae); (V) Brix (X.laevis) and BRX1 (S. cerevisiae); and (VI) RPF2 (S.cerevisiae).Typically, a protein sequence belonging to the Brix domain superfamily contains a highly charged N-terminal segment (about 50 residues) followed by a single copy of the Brix domain and another highly charged C-terminal region (about 100 residues). The archaean sequences have two unique characteristics: (1) the charged regions are totally absent at the N terminus and are reduced in number to about 10 residues at the C terminus; and (2) the C-terminal part of the Brix domain itself is minimal. Two eukaryote groups have large insertions within the C-terminal region: about 70 residues in the group III and about 120 in the group II. Biological data for some proteins in this family suggest a role in ribosome biogenesis and rRNA binding [, , , ].
