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. 2020 Dec 9;9:e64415. doi: 10.7554/eLife.64415

Figure 3. Alternative phosphate binding sites in αβα sandwich enzymes.

Figure 3.

HUP proteins are αβα sandwich proteins with a Rossmann-like strand topology. The canonical HUP phosphate binding loop is located at the tip of α1 and colored magenta (left panels; NAD+ synthase; ECOD F-group 2005.1.1.13; shown is domain e1xngA1) as in Rossmann and P-loop NTPases (Figure 2). However, Usp (universal stress proteins) is a HUP family that exhibits kinase activity wherein phosphate binding migrated to the tip of α4 (right panels; ECOD F-group 2005.1.1.145; shown is domain e2z08A1; residues interacting with phosphate groups are colored magenta). As shown in the overlay (middle panels), despite the variation in the phosphate binding site, the ribose and adenine binding modes are identical.