Figure 2: LTR2 catalyses isomerization of OsIAA11 peptide.

(a) Top: the structural features of Aux/IAA proteins. Domains I through IV are highlighted as boxes. Bottom: the alignment of partial sequences in domain II of rice and Arabidopsis Aux/IAAs. Amino-acid residues in OsIAA13 and AtIAA7 that differed with those of OsIAA11 are highlighted in blue. (b,c) Selected region of the 110 ms mixing time ROESY spectra of the OsIAA11 peptide in the absence (b) and the presence (c) of LRT2 recombinant protein. Signals from the major conformers of residues V102, W104, V107 and R108 are labelled at the positions where exchange cross peaks are expected. (d) Approximate two-state exchange process of the OsIAA11 peptdide. The exchange rate is indicated by the thickness of the double-arrow lines. * indicates the mix populations of the T¹⁰⁵T¹⁰⁶+T¹⁰⁵C¹⁰⁶ and C¹⁰⁵T¹⁰⁶+C¹⁰⁵C¹⁰⁶ obtained from the integration of the H_ɛ1 signals of W104 in the 1D ¹H spectrum, respectively, with T¹⁰⁵T¹⁰⁶ and C¹⁰⁵T¹⁰⁶ as major conformers. (e) Dependence of cross/diagonal peak intensity ratios on ROE mixing time in the presence of LRT2 for H_ɛ1 of residue W104 of the OsIAA11 peptide. Intensities of diagonal peaks with trans and cis conformations are labelled as I_tt and I_cc, respectively. The intensities of exchange peaks resulting from the LRT2-catalysed trans-to-cis and cis-to-trans isomerization are labelled as I_tc and I_ct, respectively. Catalysed exchange rate constant k_ex^cat was derived from data points fitted to equation (2) in Methods.