CLONING AND CHARACTERIZATION OF A MEMBER OF THE MST SUBFAMILY OF STE20-LIKE KINASES

We have identified a second human homolog of the yeast Ste20 protein k inase family, which we designate MST2. MST2 is most similar to the pre viously identified MST1 protein kinase (78% identity, 88% similarity). Northern analysis indicates that MST2 mRNA is expressed at high level s in adult kidney, skeletal and placental tissues and at very low leve ls in adult heart, lung, liver and brain tissues. An in vitro kinase a ssay indicates that MST2 can phosphorylate an exogenous substrate, as well as itself, and phospho-amino-acid analysis indicates that it is a serine/threonine protein kinase. The identification of MST2 suggests that there may be subfamilies of Ste20-like protein kinases and that M ST1 and MST2 may define one of these subfamilies.