RPP30

RPP30 is a protein subunit of the RNase P ribonucleoprotein complex that activates the catalytic RNA responsible for 5′ maturation of pre-tRNA (PMID:20139629, PMID:17207566). Across archaeal and protist orthologs, RPP30 assembles with Pop5 into a tight heterotetramer with 1:1 stoichiometry (two copies each of RPP30 and Pop5), with the RPP30 binding surface mapped directly to Pop5 (PMID:22162665). RPP30 adopts a TIM-barrel fold while Pop5 adopts an RRM-like fold (PMID:25704799). Functionally, RPP30 and Pop5 act on the C-domain of RNase P RNA, equivalent to the bacterial C5 protein, to activate pre-tRNA cleavage (PMID:20139629); within the heterotetramer Pop5 recognizes the SL3 stem-loop of RNase P RNA through its C-terminal α4 helix, while RPP30 itself has little affinity for SL3 and instead assists Pop5 in attaining a catalytically active conformation by shielding hydrophobic surfaces (PMID:26152732). Beyond this RNase P assembly role, no additional cellular functions of RPP30 have been characterized in the available corpus.

1. 2006 Medium

   Establishing that a Rpp30/Rpp1 homolog is a genuine subunit of the eukaryotic-type RNase P holoenzyme rather than a peripheral factor was needed to extend the RNase P protein model beyond bacteria.

   Evidence Immunochemical co-purification of Dictyostelium DRpp30 with RNase P active fractions plus in vitro RNA binding and homology modeling

   PMID:17207566

   Open questions at the time

   • Does not define stoichiometry or the precise RNA target
   • RNA binding shown in vitro without functional cleavage requirement
   • No structural data
2. 2010 Medium

   Resolved which RNase P proteins act on which RNA domain, showing RPP30 and Pop5 functionally substitute for the bacterial C5 protein in activating the catalytic C-domain.

   Evidence Chimeric RNase P RNA reconstitution with exchanged C-/S-domains and pre-tRNA cleavage assays in an archaeal system

   PMID:20139629

   Open questions at the time

   • Does not resolve the physical RPP30–Pop5 architecture
   • Mechanism of conformational activation not addressed
   • Single lab, single study
3. 2011 High

   Defined the physical architecture of the RPP30–Pop5 module, fixing its stoichiometry as a heterotetramer and mapping the RPP30 binding surface.

   Evidence NMR chemical shift perturbation mapping with orthogonal ITC, SEC, and light scattering on Pyrococcus furiosus proteins

   PMID:22162665

   Open questions at the time

   • Does not show how the tetramer engages RNase P RNA
   • No catalytic readout linking the interface to activity
4. 2015 Medium

   Established the division of labor within the heterotetramer: Pop5 recognizes RNase P RNA stem-loop SL3 via its α4 helix while RPP30 acts as a conformational chaperone for Pop5.

   Evidence SPR binding, site-directed mutagenesis of Pop5, and gel filtration in the Pyrococcus horikoshii system

   PMID:26152732

   Open questions at the time

   • RPP30's direct contribution to RNA contact remains minimal/undefined
   • Conformational shielding inferred rather than structurally captured
   • Single lab
5. 2015 High

   Provided atomic-resolution confirmation of the folds, defining RPP30 as a TIM-barrel and Pop5 as RRM-like, and demonstrated cross-species functional interchangeability.

   Evidence X-ray crystallography of TkoRpp30 alone and with TkoPop5 plus in vitro RNase P reconstitution and pre-tRNA cleavage

   PMID:25704799

   Open questions at the time

   • No structure of the full RNase P holoenzyme with RNA
   • Catalytic mechanism of cleavage not resolved at this interface

• How the RPP30–Pop5 module is integrated into the complete human RNase P holoenzyme and any roles of RPP30 outside tRNA processing remain uncharacterized in this corpus.
• No human holoenzyme structure in the corpus
• No cellular or physiological phenotype data
• No disease association established