Putative hybrid β-propeller. The YP_001558799.1 hypothetical protein from Clostridium phytofermentans (Interpro accession A9KRI6) is an example of a putative Asp-box/Reg_prop hybrid β-propeller. A single blade (blade 2) of a fold recognition model is shown along with a schematic of the sequence. The putative hybrid propeller boundaries suggested by fold recognition are marked by stippled purple frames and the likely boundaries of the blades are indicated by vertical lines. The Reg_Prop repeats are colored pink, the Asp-box repeats are light blue and residues not belonging to any of these motifs are grey. The structural model is in cartoon representation with the side chain of the tryptophan in the 10th position of the Asp-box (W111) shown in sticks. It is based on 2cn2 and is probably rather inaccurate in most respects (sequence id. 15%), but it illustrates well how the two motifs are likely to be arranged in special hybrid propeller blades. The fourth strand is missing in the modeled blade, which may appear to indicate that the model is erroneous in this area, but a lack of the fourth strand is indeed quite commonly observed for Asp-box β-propeller blades.
Quistgaard and Thirup BMC Structural Biology 2009 9:46 doi:10.1186/1472-6807-9-46