tailieunhanh - Báo cáo khoa học: Helix mobility and recognition function of the rat thyroid transcription factor 1 homeodomain – hints from 15N-NMR relaxation studies

The backbone dynamics of the 15 N-labeled homeodomain of the rat thy-roid transcription factor 1 has been studied by 2D NMR spectroscopy. Longitudinal (R1 ) and transverse (R2 ) 15 N relaxation rate constants and steady-state { 1 H}– 15 N NOEs were measured at T. | ỊFEBS Journal Helix mobility and recognition function of the rat thyroid transcription factor 1 homeodomain - hints from 15N-NMR relaxation studies Devrim Gumral Luana Nadalin Alessandra Corazza Federico Fogolari Giuseppe Damante Paolo Viglino and Gennaro Esposito Dipartimento di Scienze e Tecnologie Biomediche University di Udine Italy Keywords backbone dynamics model-free approach NMR 15N relaxation spectraldensity mapping thyroid transcription factor 1 homeodomain Correspondence G. Esposito Dipartimento di Scienze e Tecnologie Biomediche University di Udine Kolbe 4 33100 Udine Italy Fax 39 0432494301 Tel 39 0432494321 E-mail gesposito@ Received 20 October 2007 revised 25 November 2007 accepted 28 November 2007 doi 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 T. These data were analyzed by both the model-free formalism and the reduced spectral density mapping RSDM approaches. The global rotational correlation time sm of the thyroid transcription factor 1 homeodomain in aqueous solution at 286 K was found to be ns by model-free formalism and ns by RSDM calculation. The homogeneity of the values of the overall correlation time calculated from the individual RyR ratios suggested a good degree of isotropy of the global molecular motion consistent with the similar global sm 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-termi-nal portion with slightly different limits between rigid and mobile moieties. Additionally Arg53 .