Catalyzes the ATP-dependent ligation of L-glutamate and L-cysteine and participates in the first and rate-limiting step in glutathione biosynthesis. ATP + L-cysteine + L-glutamate = ADP + gamma-L-glutamyl-L-cysteine + H(+) + phosphate Feedback inhibition by glutathione. Sulfur metabolism; glutathione biosynthesis; glutathione from L-cysteine and L-glutamate: step 1/2. Heterodimer of a catalytic heavy chain and a regulatory light chain. The disease is caused by variants affecting the gene represented in this entry. Belongs to the glutamate--cysteine ligase type 3 family.