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Human dihydrofolate reductase is a substrate of protein kinase CK2α

ABSTRACT: Dihydrofolate reductase (DHFR) is a prominent molecular target in antitumor, antibacterial and antiprotozoan chemotherapies. Our in silico amino acid sequence and 3D structure analyses revealed the presence of several putative CK2 phosphorylation sites. Indeed, CK2α subunit phosphorylated DHFR in vitro. In order to identify phosphorylation site we used site-directed mutagenesis to obtain several DHFR mutants with predicted CK2-phosphorylable serine or threonine residues substituted with alanines. All enzyme forms were subjected to in vitro phosphorylation by CK2α subunit. The results pointed to serine 168. Mass spectrometry analyses revealed the presence of additional phosphoserine 145. Phosphorylation by CK2α of S145A mutant and lack of phosphorylation of S145A/S168A double mutant may indicate that S145 phosphorylation may occur only when serine 168 is already phosphorylated. The effect of these and other mutations on enzyme catalytic activity was also investigated.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Dominik Cysewski