Fig. 4

Bioinformatics characteristics of NPM2 protein. A–C Homology comparison of NPM2-core amino acid sequences. A The homology comparison result is shown as ribbons. The red, white, and blue areas represent conserved, average, and variable sequences of NPM2 protein, respectively. B, C The homology comparison result is shown as surfaces. D–G Predicted binding pockets of NPM2-core. D The result of predicted binding pockets is shown as ribbons. E–G The results of predicted binding pockets 1–3 are shown as surfaces. H–J Prediction diagram of NPM2 binding to histone H2A-H2B dimers. ZdockServer online tool (https://zdock.umassmed.edu/) was used to predict the binding between NPM2 protein and histone H2A-H2B dimers. H The prediction result is shown as ribbons. The blue, yellow, and green areas represent histone H2A, histone H2B, and NPM2, respectively. I, J The prediction result is shown as surfaces. K, L A decamer model for NPM2-core. K A side view of a modeled NPM2-core decamer is shown as ribbons. Side chains of Glu57 and Gln84 within the interface are shown as sticks. L The side chain of Glu57 in the AKEE loop would allow the formation of hydrogen bonds between Glu57 and Gln84 in opposing subunits in the modeled NPM2 decamer. M–O Side view of NPM2 pentamer/decamer binding to histones. M The structure of NPM2 pentamer. The yellow area is the core region of the NPM2 pentamer, and the red area represents the acidic region of NPM2-A2. N NPM2 pentamer binds to histone H2A-H2B dimers. The blue area represents the H2A-H2B dimers. O NPM2 decamer binds a mixture of H2A-H2B dimers and H3-H4 tetramers to form histone octamers on the chaperone. The purple area represents the H3-H4 tetramer