BIOL2117 Lecture 8: Protein Modification and Turnover (and the cell cycle)
Document Summary
Protein modification and turnover (and the cell cycle) Remember: protein modifications and turnover have broad roles in many aspects of cell biology. Cdc2 (a cdk protein) is present at similar abundance throughout the cell cycle - unlike cyclins. But cdc2 is phosphorylated during the m phase - may be activated by this. Know aas don"t have any phosphates, so to be tagged by a phosphate tag means it must be phosphorylated. A protein modification where phosphate is added to the -oh group of amino acid residues of proteins. Can occur on serine, threonine and tyrosine residues. Phosphorylation is catalysed by a class of enzymes termed kinases. Phosphatases cleave the phosphate off these groups so it can return to its dephosphorylated state. Cdks have a "t-loop" (activated group) that contains a conserved threonine residues. Cyclin binding causes a structural change in the cdks that exposes the threonine residue of the t-loop. T-loop threonine of cdk can be phosphrylated after cyclin binding.
