Ack1 kinase domain Ack1 kinase+SH3 Crystallization conditions 22–24% PEG 3350, 0.2 M Ammonium sulfate, 0.1 M bis-tris pH 6.6, 10–20mM TCEP (pH 7), 13°C 12–15% PEG 400, ... .1 M Bicine pH 9, 25 mM TCEP (pH 7) Data collection Beamline APS 17ID APS 17ID Resolution 1.31 3.23 Space group P2 1 P4 Unit cell parameters (Å, o ) 71.1, 42.3, 92.6; β = 98.6 145.5, 145.5, 103.7 Contents of the asymmetric unit Two kinase domains Four kinase+SH3 domains Measured reflections 472,369 227,669 Unique reflections 124,856 34,878 Data redundancy 3.7 6.5 Data completeness (%) 97.7 (93.6) 99.5 (96.7) R merge 0.107 (0.581) 0.187 (0.477) I/σ 11.2 (2.3) 9.9 (2.0) Refinement R work /R free (%) 19.5/20.9 24.6/27 Number of protein atoms 4,270 10,200 Number of non-protein molecules 496 water, 2 SO 4 −2 , 2 ethylene glycol 0 RMSD, bond lengths (Å) 0.003 0.009 RMSD, bond angles ( o ) 0.8 1.1 PDBID 4HZR 4HZS All the known crystal structures of the Ack1 kinase domain belong to four different crystal forms and yet all, including the one reported here, display the same packing of the two molecules in the asymmetric unit.