The ATP-dependent protease. Clp P from Esehaichia coli has been increase the stahility with or without detergent as Triton X-100 and NP-40 in the Clp P. The C]p P proteolytic activity was remained to 0.1 M salt by $Na^{-1}$, $K^{+}$, $Li^{+}$ but was inhihited by $SO_4^{2}$. An active ATPase site in Clp A is required for A TP-dependent proteolysis by Clp protease as <inalysis of ATPase activity of Clp A with Clp P treated hy diisopropyilluorophosphate. When C]p A and Clp P are mixed and applied to a gel filtration column in the ahsence of ATP. they emerge independently of each other. However, inclusion of A TP and Mg causes Clp P to appear with C]p A in a complex with over 300.000 molecular weight. The calculations suggest that the two components are present in the active complex in the r<itio of ] hexamer of Clp P to I dimer or trimer of Clp A.