In vitro inhibitor activity. For ASK in vitro kinase assays, purified GST-ASK fusion proteins were incubated with MBP as a substrate and [γ-32P]-ATP as a co-substrate in absence (−) or presence of 10 μM of the different compounds (the numbers correspond to Figure 2). Compounds 1 to 9 (left panel) differ in the aliphatic side chain. The influence of the position of the heterocyclic nitrogen was tested with compounds 3 and 11 (middle panel; the molecular structure shown represents compound 11). The right panel shows the effect of the halogen substituent of the pyridine ring. BIK, bikinin.