Table 2. Experimental Evidence Supporting the Proposed Modes of Binding of Plant IDPs.

Proposed Modes of Binding	Experimental Evidence	Reference
Entirely disordered IDPs bind to:	(I) Dehydrins bind metal ions using a specific motif containing His residues.	Heyen et al. (2002); Hara et al. (2005)
Metal ions (Figure 3A, I)	Ts-DHN-1 and -2 undergo disorder-to-order transition upon binding to zinc ion to form mainly β-strand.	Rahman et al. (2011b)
Membrane (Figure 3A, II)	(II) The K-segments of DHN1 adopt α-helices upon binding to model membranes.	Koag et al. (2003, 2009)
	Ts-DHN-1 and -2 and LEA18 bind to model membranes and fold mainly into β-strands.	Rahman et al. (2010); Hundertmark et al. (2011)
Protein partners (Figure 3A, III)	(III) Lj-IDP1 effectively protects model enzymes against stress-induced inactivation and shows propensity of folding into α-helix.	Haaning et al. (2008)
Differential effects of phosphorylation (Figure 3A, IV)	(IV) Phosphorylation has differential effects on interactions between IDPs and partners. It can activate, enhance, or prevent binding of dehydrins to metal ions and membranes.	Alsheikh et al. (2005); Rahman et al. (2011a); Eriksson et al. (2011)
Partly disordered plant IDPs without intramolecular interaction between the disordered and ordered domains bind to protein partners (Figure 3B, I)	(I) The subgroup-specific conserved motifs in the disordered TRDs of NAC TFs most likely serve as molecular recognition sites and interact with specific and general proteins of the transcriptional apparatus.	Taoka et al. (2004); Jensen et al. (2010); Kjaersgaard et al. (2011)
	The disordered N-terminal domain of HY5 interacts with COP1 to negatively regulate the level and activity of HY5.	Ang et al. (1998); Hardtke et al. (2000)
Differential effects of phosphorylation (Figure 3B, II)	(II) Phosphorylation can either promote or obstruct the interactions between the disordered domains and their partners. Phosphorylation at several sites enables Sic1 (an inhibitor of a cyclin dependent kinase) to bind to Cdc4 (a subunit of an ubiquitin ligase). Conversely, phosphorylation weakens binding between the disordered N-terminal domain of HY5 and COP1.	Mittag et al. (2010); Hardtke et al. (2000)
Partly disordered plant IDPs with intramolecular interaction between the disordered and ordered domains Disordered domain releases an active site of the ordered domain (Figure 3C, I)	(I) dCRY dissociates its disordered C-terminal domain from the PHR so that TIM can bind to the PHR domain of dCRY preoccupied by the C-terminal domain for its subsequent ubiquitin-mediated degradation. Here, the short C-terminal domain of dCRY contributes to regulation of the circadian clock by determining availability of the active site in the PHR domain to TIM.	Busza et al. (2004); Dissel et al. (2004); Koh et al. (2006)
Disordered domains fold alternatively for binding to protein partners (Figure 3C, II)	(II) Light-driven release of the C-terminal domain of At-CRYs from the PHR domain results in direct interaction between the C-terminal domain of CRY and COP1, which initiates the downstream photomorphogenic program. Here, the long C-terminal domain of CRY contributes to plant photomorphogenesis by alternative folding to directly bind to COP1.	Yang et al. (2000, 2001); Wang et al. (2001); Partch et al. (2005)
The release of disordered domains free the active sites of both ordered and disordered domains (Figure 3C, III)	(III) Light-driven dissociation of the C-terminal domain from the PHR of full-length At-CRY1 leads to exposure of the previously buried interaction sites in both the PHR and the C-terminal domain, indicating the potential simultaneous interactions of different partners or effectors with both the PHR and the C-terminal domain of CRY1.	Kondoh et al. (2011)
	The disordered N-domains of DELLA subfamily of GRAS proteins were suggested to mask the active site in the GRAS domain that is responsible for interaction with the F-box proteins to target DELLA proteins for 26S proteasomal degradation in response to GA signal. Upon perceiving GA signal, the DELLA motif (α-MoRFs) and the VHYNP motif (ι-MoRFs) in the N-domains of DELLA proteins fold and bind to the GA receptor GID1, which may make the active site in the GRAS domain accessible to the F-box proteins.	Murase et al. (2008); Sun et al. (2010); Sheerin et al. (2011)