Figure 5.

Hsd subunits were monitored, after treatment with 2-AP, using antibodies raised against the relevant R-M complex. HsdR is degraded only when it is a part of a functional complex. (a) Degradation of HsdR is prevented by a missense mutation in hsdR (track 5) or by the absence of HsdM and S (track 8). (b) The presence of functional EcoAI has no effect on the degradation of the HsdR subunit of EcoKI (Upper), even though the HsdR subunit of EcoAI itself is degraded (Lower, lanes 2, 5, and 8). The control tracks for EcoAI contain a mixture of polypeptides in which HsdM and HsdS are present in molar excess to give strong signals with antibody.