gamma-L-glutamyl-L-glutamyl-[tubulin] + L-glutamate + ATP = L-glutamyl-gamma-L-glutamyl-L-glutamyl-[tubulin] + ADP + phosphate + H(+)
gamma-l-glutamyl-l-glutamyl-[tubulin] + l-glutamate + atp = l-glutamyl-gamma-l-glutamyl-l-glutamyl-[tubulin] + adp + phosphate + h(+)