Figure 5: A proposed model for the LRT2-regulated auxin signalling.

The OsIAA11 transcriptional repressor is present as two exchangeable major conformers T¹⁰⁵T¹⁰⁶ and C¹⁰⁵T¹⁰⁶ (indicated by a thin double-arrowed line). The cyclophilin LRT2 catalyses the peptidyl-prolyl cis/trans isomerization at Trp¹⁰⁴–Pro¹⁰⁵ peptide bond of OsIAA11, accelerating the formation of the Pro¹⁰⁵-cis conformer (indicated by a thick double-arrowed line). In the presence of auxin (red molecule), C¹⁰⁵T¹⁰⁶ conformers interact with the SCF^TIR1 complex with a higher affinity than T¹⁰⁵T¹⁰⁶ conformers. The formation of the SCF^TIR1-OsIAA11 co-receptor facilitates the ubiquitination and subsequent proteasomal degradation of OsIAA11, which consequently leads to the two-state equilibrium shifting in favour of the formation of C¹⁰⁵T¹⁰⁶ conformers. Domains I through IV are indicated in the OsIAA11 molecule.