The Structurally Plastic CH2 Domain Is Linked to Distinct Functions of Fimbrins/Plastins.
Fimbrins/plastins have been implicated in the generation of distinct actin structures, which are linked to different cellular processes. Historically, fimbrins/plastins were mainly considered as generating tight actin bundles. Here, we demonstrate that different members of the fimbrin/plastin family have diverged biochemically during evolution to generate either tight actin bundles or loose networks with distinct biochemical and biophysical properties. Using the phylogenetically and functionally distinct Arabidopsis fimbrins FIM4 and FIM5 we found that FIM4 generates both actin bundles and cross-linked actin filaments, whereas FIM5 only generates actin bundles. The distinct functions of FIM4 and FIM5 are clearly observed at single-filament resolution. Domain swapping experiments showed that cooperation between the conformationally plastic calponin-homology domain 2 (CH2) and the N-terminal headpiece determines the function of the full-length protein. Our study suggests that the structural plasticity of fimbrins/plastins has biologically meaningful consequences, and provides novel insights into the structure-function relationship of fimbrins/plastins as well as shedding light on how cells generate distinct actin structures.
From the Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, the University of Chinese Academy of Sciences, Beijing 100049, China.
Ruihui
R
Zhang
the Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084.
Ming
M
Chang
From the Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, the University of Chinese Academy of Sciences, Beijing 100049, China.
Meng
M
Zhang
From the Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093.
Youjun
Y
Wu
the Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, the Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084, and.
Xiaolu
X
Qu
From the Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, the Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, sjhuang@tsinghua.edu.cn.
Shanjin
0000-0001-9517-2515
S
Huang
D008841:Actin Cytoskeleton / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000072417:Protein Domains
D029681:Arabidopsis Proteins; D008562:Membrane Glycoproteins; D008840:Microfilament Proteins; C026742:plastin
Arabidopsis; Arp2/3 complex; actin; cytoskeleton; microfilaments; plant