The Bacillus subtilis RNase P holoenzyme contains two RNase P RNA and two RNase P protein subunits
Fang, X.W.; Yang, X.J.; Littrell, K.; Niranjanakumari, S.; Thiyagarajan, P.; Fierke, C.A.; Sosnick, T.R.; Pan, T.
Rna 7(2): 233-241
ISSN/ISBN: 1355-8382 PMID: 11233980 Accession: 011465316
Ribonuclease P (RNase P) catalyzes the 5' maturation of precursor tRNA transcripts and, in bacteria, is composed of a catalytic RNA and a protein. We investigated the oligomerization state and the shape of the RNA alone and the holoenzyme of Bacillus subtilis RNase P in the absence of substrate by synchrotron small-angle X-ray scattering and affinity retention. The B. subtilis RNase P RNA alone is a monomer; however, the scattering profile changes upon the addition of monovalent ions, possibly suggesting different interdomain angles. To our surprise, the X-ray scattering data combined with the affinity retention results indicate that the holoenzyme contains two RNase P RNA and two RNase P protein molecules. We propose a structural model of the holoenzyme with a symmetrical arrangement of the two RNA subunits, consistent with the X-ray scattering results. This (P RNA)2(P protein)2 complex likely binds substrate differently than the conventional (P RNA)1 (P protein)1 complex; therefore, the function of the B. subtilis RNase P holoenzyme may be more diverse than previously thought. These revisions to our knowledge of the RNase P holoenzyme suggest a more versatile role for proteins in ribonucleoprotein complexes.