Overexpression and spectroscopic characterization of a recombinant human tumor suppressor p16^INK4

p16^INK4, which is a 16-kDa polypeptide protein, inhibits the catalytic activity of the CDK4-cyclinD complex to suppress tumor growth. Both unlabeled and isotopelabeled human tumor suppressor p16^INK4 protein were overexpressed and purified to characterize biochemical and structural properties. The purified p16 binds to monomeric GST-CDK4 and exists in a monomer conformation for several weeks at 4°C. The circular dichroism (CD) data indicates that p16 contains high percentage of α-helix and that the helix percentage maximized at pH value of 7.0. One- and two-dimensional nuclear magnetic resonance (NMR) data suggest that purified p16 from our construct has a unique folded conformation under our experimental conditions and exhibits quite stable conformational characteristics.