8WAG

Crystal structure of the C-terminal fragment (residues 716-982) of Arabidopsis thaliana CHUP1

Summary for 8WAG

• Entry DOI: 10.2210/pdb8wag/pdb
• Related: 6L2X
• Descriptor: Protein CHUP1, chloroplastic (1 entity in total)
• Functional Keywords: actin, actin nucleator, chloroplast movement, chloroplast unusual positioning 1, plant protein
• Biological source: Arabidopsis thaliana (thale cress)
• Total number of polymer chains: 2
• Total formula weight: 61337.64

Authors

Shimada, A.,Nakamura, Y.,Takano, A.,Kohda, D. (deposition date: 2023-09-07, release date: 2024-01-17, Last modification date: 2024-04-10)

Primary citation

Kong, S.G.,Yamazaki, Y.,Shimada, A.,Kijima, S.T.,Hirose, K.,Katoh, K.,Ahn, J.,Song, H.G.,Han, J.W.,Higa, T.,Takano, A.,Nakamura, Y.,Suetsugu, N.,Kohda, D.,Uyeda, T.Q.P.,Wada, M.
CHLOROPLAST UNUSUAL POSITIONING 1 is a plant-specific actin polymerization factor regulating chloroplast movement.
Plant Cell, 36:1159-1181, 2024

PubMed Abstract: Plants have unique responses to fluctuating light conditions. One such response involves chloroplast photorelocation movement, which optimizes photosynthesis under weak light by the accumulation of chloroplasts along the periclinal side of the cell, which prevents photodamage under strong light by avoiding chloroplast positioning toward the anticlinal side of the cell. This light-responsive chloroplast movement relies on the reorganization of chloroplast actin (cp-actin) filaments. Previous studies have suggested that CHLOROPLAST UNUSUAL POSITIONING 1 (CHUP1) is essential for chloroplast photorelocation movement as a regulator of cp-actin filaments. In this study, we conducted comprehensive analyses to understand CHUP1 function. Functional, fluorescently tagged CHUP1 colocalized with and was coordinately reorganized with cp-actin filaments on the chloroplast outer envelope during chloroplast movement in Arabidopsis thaliana. CHUP1 distribution was reversibly regulated in a blue light- and phototropin-dependent manner. X-ray crystallography revealed that the CHUP1-C-terminal domain shares structural homology with the formin homology 2 (FH2) domain, despite lacking sequence similarity. Furthermore, the CHUP1-C-terminal domain promoted actin polymerization in the presence of profilin in vitro. Taken together, our findings indicate that CHUP1 is a plant-specific actin polymerization factor that has convergently evolved to assemble cp-actin filaments and enables chloroplast photorelocation movement.

PubMed: 38134410
DOI: 10.1093/plcell/koad320

Experimental method

X-RAY DIFFRACTION (3.003 Å)