Protein kinase transfer the terminal phosphate from ATP to specific serines, threonines or tyrosines of specific target proteins. To test these particular phosphorylation sites we use site-directed mutagenesis to convert the to-be-phosphorylated serines, threonines or tyrosines to aspartic acids or alanines. One of these is considered a non-phosphorylatable mutation and the other is a phospho-mimetic mutation.
Which type of amino acid replacements is a non-phosphorylatable or a phospho-mimetic?
Explain your answer.