Acts as a cytosolic iron-sulfur (Fe-S) cluster assembly factor that facilitates [2Fe-2S] cluster insertion into a subset of cytosolic proteins (PubMed:26613676, PubMed:27519415). Acts together with the monothiol glutaredoxin GLRX3 (PubMed:26613676, PubMed:27519415). {ECO:0000269|PubMed:26613676, ECO:0000269|PubMed:27519415}. This is the function of BOLA2B (bolA family member 2B, ENSG00000169627).