These results suggested that the variable domain and β-sandwich module, besides the β-propeller module, are important for inulin-degrading activity of LevH1.
Each β-propeller module consists of four antiparallel β-strands that form a sheet warped like a propeller blade (see Figure 1B).
The inferred 3D structures of the proteins encoded by Ceratocystidaceae GH32 genes further confirmed the presence of the five-bladed β-propeller catalytic module at the N-terminal, as well as the presence of two six-stranded β-sheets composed of antiparallel β-strands forming a sandwich-like fold at the C-terminal domain (Fig. 3).
The crystal structure of the Cys249Ser mutant revealed that the 254-residue protein chain is arranged like a propeller with five pseudosimilar modules as blades, each comprised of a three-stranded β-sheet packed against an α-helix.
Additionally, the WD40 repeat propeller structure is an adaptable module that can recognize particular post-translational modifications (Stirnimann et al., 2010; Xu and Min, 2011).
In the crystal structure at pH = 5.3, the ligand-binding domain (modules R2 to R7) folds back as an arc over the epidermal growth factor precursor homology domain (the modules A, B, β propeller, and C).
The Med16 N-terminal β-propeller is centrally located in the Tail module and forms extensive interactions with Med5.
The localizations of the eIF3b β propeller, the eIF3b-RRM, and the PCI modules of eIF3a and eIF3c have a precision of <30 Å and are the best-defined components within our modeling solutions (Table S6 and Figure 6C).
This fold similarity, analyzed initially in yeast, led to the "protocoatomer hypothesis," which proposes that a simple membrane-curving module, made primarily from β-propeller and α-solenoid folds, was a common ancestor for NPCs and coated vesicles that originated in the precursors to the ancient last ancestor common to all eukaryotes (Devos et al. 2004, 2006; Alber et al. 2007a, b).
High resolution structures of the mouse PIEZO1 protein were recently obtained revealing a trimeric three-bladed, propeller-shaped structure with a central pore-forming module comprising of an outer helix (OH), C-terminal extracellular domain (CED), inner helix (IH), and intracellular C-terminal domain (CTD 21,22,23.
