Structural plasticity and Mg2+ binding properties of RNase P P4 from combined analysis of NMR residual dipolar couplings and motionally decoupled spin relaxation.

Published

Journal Article

The P4 helix is an essential element of ribonuclease P (RNase P) that is believed to bind catalytically important metals. Here, we applied a combination of NMR residual dipolar couplings (RDCs) and a recently introduced domain-elongation strategy for measuring "motionally decoupled" relaxation data to characterize the structural dynamics of the P4 helix from Bacillus subtilis RNase P. In the absence of divalent ions, the two P4 helical domains undergo small amplitude (approximately 13 degrees) collective motions about an average interhelical angle of 10 degrees. The highly conserved U7 bulge and helical residue C8, which are proposed to be important for substrate recognition and metal binding, are locally mobile at pico- to nanosecond timescales and together form the pivot point for the collective domain motions. Chemical shift mapping reveals significant association of Mg2+ ions at the P4 major groove near the flexible pivot point at residues (A5, G22, G23) previously identified to bind catalytically important metals. The Mg2+ ions do not, however, significantly alter the structure or dynamics of P4. Analysis of results in the context of available X-ray structures of the RNA component of RNase P and structural models that include the pre-tRNA substrate suggest that the internal motions observed in P4 likely facilitate adaptive changes in conformation that take place during folding and substrate recognition, possibly aided by interactions with Mg2+ ions. Our results add to a growing view supporting the existence of functionally important internal motions in RNA occurring at nanosecond timescales.

Full Text

Duke Authors

Cited Authors

  • Getz, MM; Andrews, AJ; Fierke, CA; Al-Hashimi, HM

Published Date

  • February 2007

Published In

Volume / Issue

  • 13 / 2

Start / End Page

  • 251 - 266

PubMed ID

  • 17194721

Pubmed Central ID

  • 17194721

Electronic International Standard Serial Number (EISSN)

  • 1469-9001

International Standard Serial Number (ISSN)

  • 1355-8382

Digital Object Identifier (DOI)

  • 10.1261/rna.264207

Language

  • eng