DnaJ (Hsp40) Homolog, Subfamily B, Member 4 (DNAJB4) is a member of the evolutionarily conserved DNAJ/HSP40 protein family. DNAJB4 subunit configuration is homodimer. DNAJB4 possibly functions as a chaperone. DNAJB4 C-terminal section interacts with the C-terminal tail of OPRM1. DNAJB4 also has an interaction with SDIM1. DNAJB4 is expressed in the heart, pancreas and skeletal muscle, and to a lesser extent in the brain, placenta and liver.