(Ruderman and Beach). Frog-specific cyclin antibodies (Tim Hunt) recognized the 45kDa component in Maller s MPF prep. Stage VI What are the protein components of MPF? Where was the catalytic subunit of MPF identified? What distinguishing characteristics of cyclins made them stand out? How was it demonstrated that cyclin is necessary and sufficient for driving frog interphase extracts into mitosis? How is cyclin normally destroyed? What stage of mitosis is cyclin B normally destroyed in? Where do mitotic extracts expressing a non-degradable form of cyclin arrest? What E3 ligase is responsible for cyclin B degradation? 1. Level of Cdc2 does not change 2. Activity changes dramatically—-late G2 just prior to Mitosis see activation What is keeping it off and what is turning it on? Is cyclin binding all that is required?