Jun 24, 2011· STO-609 inhibits both the CaMKKα and the CaMKKβ isoforms, but CaMKKβ is more sensitive to STO-609 than CaMKKα . The CaMKKβ·STO-609 complex structure determined in this study provides a basis for understanding the selective inhibition of CaMKKβ by STO-609 as compared with CaMKKα and other protein kinases.