... that interfacial protein< /b> protein < /b> interactions between < /b> the < /b> hinge region of < /b> ISP and < /b> the < /b> extramembranous cd2 helix of < /b> cytochrome < /b> b are important for maintaining the < /b> structure of < /b> the < /b> hinge region and,< /b> ... also affect the < /b> binding of < /b> the < /b> ISP to the < /b> bc1 complex and < /b> distort the < /b> Qo site Our data showed that, in the < /b> mutant, the < /b> bc1 activity was severely decreased The < /b> kinetics of < /b> reduction of < /b> cytochrome < /b> ... compensatory, because, in the < /b> revertants, the < /b> bc1 activity remained low and < /b> the < /b> instability of < /b> the < /b> complex persisted, as observed for the < /b> primary mutant In order to monitor the < /b> effect of < /b> the < /b> secondary...