Catalysis of the reactions: ATP + protein serine = ADP + protein serine phosphate.
Source:RHEA:17989
Comment
Note that this term is to annotate proteins the specifically phosphorylate a serine residue on a protein. An example is human PIKFYVE (UniProt:Q9Y2I7). For dual specificity protein kinases, use 'protein serine/threonine kinase activity' ; GO:0004712.