Three-dimensional localization of recurrent JAK3- and STAT5B-mutated amino acids. (A) The crystal structure of the SH2 domain of the STAT5A protein (1y1u) highlighting analogous residues of the STAT5B mutations p.N642H (blue), p.Y665H (purple), and p.T628S (red) demonstrating close 3-dimensional proximity of recurrently mutated STAT5B residues. Colored fill indicates an identical amino acid; white, minus indicates disparate residues; white with colored text, + indicates similar residues; and selected mutated residues are indicated in red. (B) The pseudokinase domain of JAK2 (4fvp) highlighting the V617 residue (light blue) recurrently mutated in myeloproliferative neoplasms and analogous residues for JAK3 mutations p.A573V (red), p.M511I (dark blue), and p.K563_C565del (purple). The extent of homology between the STAT5A and STAT5B or JAK2 and JAK3 in the regions of these recurrently mutated residues (red arrows) is highlighted below each respective 3-dimensional structure.