Enables glutamate-cysteine ligase catalytic subunit binding activity. Acts upstream of or within several processes, including cellular response to leukemia inhibitory factor; glutathione biosynthetic process; and positive regulation of glutamate-cysteine ligase activity. Part of glutamate-cysteine ligase complex. Is expressed in several structures, including alimentary system; liver; nervous system; urinary system; and vibrissa. Human ortholog(s) of this gene implicated in myocardial infarction and vascular dementia. Orthologous to human GCLM (glutamate-cysteine ligase modifier subunit). [provided by Alliance of Genome Resources, Apr 2022]