Required for nuclear and mitochondrial iron-sulfur protein biosynthesis. Cofactor biosynthesis; iron-sulfur cluster biosynthesis. Interacts with FXN. Interaction is increased by nickel. Interaction is inhibited by calcium, magnesium, manganese, copper, cobalt, zinc, and iron. Forms a complex with the cytosolic/nuclear form of NFS1. The complex increased the stability of NFS1. Reduced mRNA levels in Friedreich ataxia patients. The disease is caused by variants affecting the gene represented in this entry. Reduction of LYRM4 levels by siRNA increases the total iron content, and reduces cytosolic and mitochondrial aconitase activities and NFS1 protein levels. Belongs to the complex I LYR family.