Molecular function

Catalysis of the reaction: histone H2AX-serine (position 139) + ATP = histone H2AX-phosphoserine (position 139) + ADP. This reaction is the addition of a phosphate group to the serine residue at position 139 of histone variant H2AX.

histone H2AS139 kinase activity, histone kinase activity (H2A-S139 specific)

Residue 1 of histone H2A is taken as the first residue following removal of the initiating Methionine (Met).