Główne pojęcia
Primary cell wall cellulose synthase (CesA) isoforms assemble into catalytically active homotrimeric complexes that can interact with each other, leading to synergistic cellulose biosynthesis.
Streszczenie
The content provides a detailed structural and functional characterization of primary cell wall cellulose synthase (CesA) isoforms from soybean (Glycine max). Key highlights:
- The three primary cell wall CesA isoforms (CesA1, CesA3, and CesA6) purify as catalytically active homotrimeric complexes, similar to secondary cell wall CesAs.
- The homotrimers exhibit differences in the positioning of transmembrane helix 7, creating a large lateral opening in the cellulose translocation channel.
- In vitro, homotrimers of different CesA isoforms can interact with each other, independent of the N-terminal domains. This interaction leads to synergistic cellulose biosynthesis.
- The class-specific region (CSR) of CesAs is proposed to mediate the inter-isoform interactions, potentially by providing distinct binding sites for different isoforms.
- The results support a model where cellulose synthase complexes (CSCs) in plants are assembled from homotrimers of different CesA isoforms, rather than heterotrimers of the same isoforms.
Statystyki
"Cellulose biosynthesis in the presence of 1.4, 0.5, and 2.3 mM UDP-Glc for GmCesA1, 3, and 6, respectively, and the indicated increasing concentrations of UDP."
"CesA1 has an apparent Vmax of approximately 0.1 nmol/(sec mg), about four and five times higher compared to CesA3 and CesA6, respectively."
"The affinities for substrate binding range from 1.4 mM for CesA1 to 0.6 and 2.4 mM for CesA3 and CesA6, respectively."
"The experimental activity of combining all three CesA isoforms is about 3-fold above the theoretical value."
Cytaty
"Contrasting secondary cell wall CesAs, a peripheral position of the C-terminal transmembrane helix creates a large, lipid-exposed lateral opening of the enzymes' cellulose-conducting transmembrane channels."
"Our data suggest that cross-isoform interactions are mediated by the class-specific region, which forms a hook-shaped protrusion of the catalytic domain at the cytosolic water-lipid interface."
"Combined, our structural and biochemical data favor a model by which homotrimers of different CesA isoforms assemble into a microfibril-producing CSC."