Figure 6. mMyo3A and 3B kinases phosphorylate the loop2 region of the myosin motor domain and the C-terminal tail of Myo3B on both serines and threonines.

The loop2 and C-terminal tail regions of mMyo3B were expressed as His-tagged proteins in E. coli, purified and used as substrates for mMyo3A and 3B kinases. A and C. Phosphorimages of SDS-PAGE gels which separated the kinases (asterisk) from the substrates (arrow head). The kinase used is indicated at the top of each pair of Phosphorimages. (−) lanes contained the kinase and no added substrate. (+) lanes contained the kinase and substrate. B and D. Phosphorimages of phosphorylated amino acids from the loop2 region of Myo3B (B) and the C-terminal of the tail of Myo3B (D). Both were phosphorylated by Myo3A kinase. Identical results were obtained following phosphorylation with the 3B kinase. The phosphoamino acids were separated by two-dimensional high voltage thin layer electrophoresis as described in the legend to Figure 2. The arrows indicate the directions of electrophoretic migration. The white circles indicate the locations of the phosphoserine (S) and phosphothreonine (T) standards.