Figure 8.

In vitro activity of the GM-6 and GM-1237 mutant proteins is not thermolabile. Affinity-purified GM-WT, GM-6, and GM-1237 kinases were assayed in vitro at 25°C and 35°C, and then separated on an SDS-PAGE gel and blotted. This elevated assay temperature would be nonpermissive for growth of both mps1–6 and mps1–1237 mutant strains. (A) Autophosphorylation activity of the proteins at both assay temperatures. (B) Substrate-level phosphorylation of myelin basic protein (MBP). For each pair of samples (25°C and 35°C), protein loadings were approximately equal (determined by Western blot).