Abstract: ALG-2 is a penta-EF-hand Ca2+-binding protein and interacts with a variety of intracellular proteins. Two types of ALG-2-binding motifs have been determined: type 1, PXYPXnYP (X, variable; n = 4), in ALIX and PLSCR3; type 2, PXPGF, in Sec31A and PLSCR3. The previously solved X-ray crystal structure of the complex between ALG-2 and an ALIX peptide containing type 1 motif showed that the peptide binds to Pocket 1 and Pocket 2. Co-crystallization of ALG-2 and type 2 motif-containing peptides has not been successful. To gain insights into the molecular basis of type 2 motif recognition, we searched for a new hydrophobic cavity by computational algorithms using MetaPocket 2.0 based on 3D structures of ALG-2. The predicted hydrophobic pocket designated Pocket 3 fits with N-acetyl-ProAlaProGlyPhe-amide, a virtual penta-peptide derived from one of the two types of ALG-2-binding sites in PLSCR3 (type 2 motif), using the molecular docking software AutoDock Vina. We investigated effects of amino acid substitutions of the predicted binding sites on binding abilities by pulldown assays using glutathione-S-transferase -fused ALG-2 of wild-type and mutant proteins and lysates of cells expressing green fluorescent protein -fused PLSCR3 of wild-type and mutants. Substitution of either L52 with Ala or F148 with Ser of ALG-2 caused loss of binding abilities to PLSCR3 lacking type 1 motif but retained those to PLSCR3 lacking type 2 motif, strongly supporting the hypothesis that Pocket 3 is the binding site for type 2 motif.
Keywords: ALG-2; calcium-binding protein; computational prediction; protein-protein interaction; proline-rich motif
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Takahashi, T.; Suzuki, H.; Inuzuka, T.; Shibata, H.; Maki, M. Prediction of a New Ligand-Binding Site for Type 2 Motif based on the Crystal Structure of ALG-2 by Dry and Wet Approaches. Int. J. Mol. Sci. 2012, 13, 7532-7549.
Takahashi T, Suzuki H, Inuzuka T, Shibata H, Maki M. Prediction of a New Ligand-Binding Site for Type 2 Motif based on the Crystal Structure of ALG-2 by Dry and Wet Approaches. International Journal of Molecular Sciences. 2012; 13(6):7532-7549.
Takahashi, Takeshi; Suzuki, Hironori; Inuzuka, Tatsutoshi; Shibata, Hideki; Maki, Masatoshi. 2012. "Prediction of a New Ligand-Binding Site for Type 2 Motif based on the Crystal Structure of ALG-2 by Dry and Wet Approaches." Int. J. Mol. Sci. 13, no. 6: 7532-7549.