Catalyzes the synthesis of gamma-glutamylcysteine (gamma-GC) (By similarity). This compound is used as substrate for the biosynthesis of the low-molecular thiol compound ergothioneine (PubMed:20420449). ATP + L-cysteine + L-glutamate = ADP + gamma-L-glutamyl-L-cysteine + H(+) + phosphate Amino-acid biosynthesis; ergothioneine biosynthesis. Belongs to the glutamate--cysteine ligase type 2 family. EgtA subfamily. Extended N-terminus.