Fig. 7: Updated schematic of the SL signalling mechanism. | Nature Communications

Fig. 7: Updated schematic of the SL signalling mechanism.

From: Mechanism of cooperative strigolactone perception by the MAX2 ubiquitin ligase–receptor–substrate complex

Fig. 7: Updated schematic of the SL signalling mechanism.

In the pre-signalling state (left), the MAX2 CTH is dislodged, as seen in apo-ASK1–MAX2 (PDB 9KLL). Strigolactone perception and hydrolysis enable HTL7 to close and bind to MAX2, trapping the D-ring in the active site. This HTL7 conformation creates the interface for SMAX1D2 to mutually stabilise the tripartite MAX2–HTL7–SMAX1D2 complex. Simultaneously, SMAX1N engages another site on the MAX2 LRR, close to the MAX2 CTH and ASK1, promoting the “retracted” position of ASK1. The transient interactions of SMAX1N lead to a tapping motion of the E2 towards SMAX1D2, while the interaction dynamics of SMAX1D2 with MAX2 lead to positional variations towards the E2. Together, these oscillating interactions flexibly position SMAX1D2 for polyubiquitination, leading to proteasomal degradation of SMAX1, thereby enabling transcription to occur.

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