The Hsp40 (heat shock protein with molecular size of approximately 40 kDa) is one of the mammalian homologues of bacterial DnaJ heat shock protein. Ohtsuka (1993) isolated a cDNA encoding a 40-kD heat-shock protein designated HSPF1. The deduced 340-amino acid HSPF1 protein is 34% identical to E. coli DnaJ and 34% and 36% identical to HSJ1 and HSJ2, respectively. HSPF1 gene spans over 7 kb and contains 3 exons and 2 introns. HSPF1 gene is mapped to chromosome 19p13.2.