Helix mobility and recognition function of the rat thyroid transcription factor 1 homeodomain - Hints from 15N-NMR relaxation studies

Devrim Gümral, Luana Nadalin, Alessandra Corazza, Federico Fogolari, Giuseppe Damante, Paolo Viglino, Gennaro Esposito

Research output: Contribution to journalArticlepeer-review

Abstract

The backbone dynamics of the 15N-labeled homeodomain of the rat thyroid transcription factor 1 has been studied by 2D NMR spectroscopy. Longitudinal (R1) and transverse (R2) 15N relaxation rate constants and steady-state {1H}-15N NOEs were measured at 11.7 T. These data were analyzed by both the model-free formalism and the reduced spectral density mapping (RSDM) approaches. The global rotational correlation time, τm, of the thyroid transcription factor 1 homeodomain in aqueous solution at 286 K was found to be 10.51 ± 0.05 ns by model-free formalism and 9.85 ± 1.79 ns by RSDM calculation. The homogeneity of the values of the overall correlation time calculated from the individual (R2/R1) ratios suggested a good degree of isotropy of the global molecular motion, consistent with the similar global τm results obtained with the two different methods. Tyr25 was found to undergo slow conformational exchange by both methods, whereas this contribution was identified also for Lys21, Gln22, Ile38 and His52 only by RSDM. With both methods, the C-terminal fragment of helix III was found to be more flexible than the preceding N-terminal portion, with slightly different limits between rigid and mobile moieties. Additionally, Arg53 appeared to be characterized by an intermediate motional freedom between the very flexible N-terminal and C-terminal residues and the structured core of the molecule, suggesting the occurrence of a hinge point. Finally, slow-time-scale motions observed at the end of helix I, at the end of helix II and within helix III appear to be consistent with typical fraying transitions at helical C-termini.

Original languageEnglish (US)
Pages (from-to)435-448
Number of pages14
JournalFEBS Journal
Volume275
Issue number3
DOIs
StatePublished - Feb 2008

Keywords

  • Backbone dynamics
  • Model-free approach
  • NMR N relaxation
  • Spectral density mapping
  • Thyroid transcription factor 1 homeodomain

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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