Chaperones substrate recognition

In every case, the chaperone substrates for ClpA and ClpX are also substrates for degradation by the respective ClpAP or ClpXP protease. For example, ClpXP degrades MuA, and ClpAP degrades RepA (Levchenko et al., 1995 Wickner et al., 1994). Thus the specificity of protein recognition resides on the ATPase component. 

Smith CK, Baker TA, Sauer RT. (1999) Lon and Clp family proteases and chaperones share homologous substrate-recognition domains. Proc Natl Acad Sci USA 96(12), 6678-6682. 

Fig. 9.4. Hypothetical reaction cycle for the 26S proteasome. A polyubiquitylated substrate is delivered to a 26S hybrid proteasome in some cases by chaperones such as VCP/p97 (step 1). Substrate is bound by polyubiquitin recognition components within the regulatory complex (RC) until the polypeptide chain is engaged by the ATPases (step 2). As the...

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