STK4 encodes a cytoplasmic kinase with a structure similar to the yeast Ste20p kinase that can phosphorylate myelin basic protein and undergoes autophosphorylation.
The protein encoded by this gene is a cytoplasmic kinase that is structurally similar to the yeast Ste20p (sterile 20 protein) kinase, which acts upstream of the stress-induced mitogen-activated protein kinase (MAPK) cascade. The encoded protein can phosphorylate myelin basic protein and undergoes autophosphorylation. 
