Dynamic flexibility of the ATPase p97 is important for its interprotomer motion transmission

The hexameric protein p97, a very abundant type II AAA ATPase (ATPase associated with various cellular activities), is involved in a diverse range of cellular functions. During its ATPase cycle p97 functions as an ATP motor, converting the chemical energy released upon hydrolysis of ATP to ADP into mechanical work, which is then directed toward the proteins that serve as substrates. A key question in this process is: How is the nucleotide-induced motion transmitted from the C-terminal ATPase domain (the D2 domain) of p97 to the distant N-terminal substrate-processing domain? We have previously reported the surprising finding that motion transmission between the two ATPase domains (the D2 and D1 domains) is mediated by the D1-D2 linker region of its neighboring protomer. In this study we report efforts to better understand this process. Our findings suggest that the amino acid sequence containing Gly-Gly that is located at the C terminus of the D1-D2 linker functions as a pivoting point that allows the dynamic movement of the D1-D2 linker. Furthermore, we found that locking the D1-D2 linker to the D2 domain by introducing disulfide bonds significantly impaired the motion-transmission process. These results support our previous model for interprotomer motion transmission, and provide more detailed information on how the motion transmission between the two ATPase domains of p97 is relayed by the flexible movement of the D1-D2 linker from its neighboring protomer.