Differences among NKG2D-mutant MICA complexes as observed in the SEC binding assay. The elution profile of UV absorbance vs. time as constant flow resulting from an injection of NKG2D alone is shown as a gray line; MICA mutant or wild-type alone is shown as a dashed line; and NKG2D and MICA mutant or wild-type mixed in 2:1 molar ratios is shown as a solid line. The elution times of size standards under identical conditions are shown above each graph. Graphs are labelled with the specific representative mutant. (a) Some mutants elute as a ~60-kDa peak (++). (b-d) Some MICA mutants and wild-type elute with an early shoulder undifferentiated from the ~30-kDa unbound peak (+). (e-f) Some MICA mutants with stabilizing mutations elute only as a ~30-kDa peak aligned with the elution time of both proteins alone (-).