Glucose regulated protein 78 ku(GRP78)was one member of heat shock protein 70(HSP70)family.As a molecular chaperone,GRP78 plays important roles in regulating the protein folding and maintaining the stability of endoplasmic reticulum.In this study,we firs cloned the full-length cDNA sequence of GRP78 from mud crab,Scylla paramamosain using RT-PCR and RACE.The full-lengty of GRP78 cDNA is 2 284 bp with 1 962 bp open reading frame encoding 653 amino acids.The homologous analysis indicated that the deduced amino acids contained the signature sequences of HSP70 and the endoplasmic reticulum retention sequence in the C-terminal domain.The deduced amino acid sequence shared high identity with previously reported GRP78s.RT-PCR indicated that GRP78 was expressed in various tissues.When S.paramamosain juveniles exposed to different temperatures and salinities after 12 hours,the expression of GRP78 gene increased with the rise of environmental temperature and a high expression of GRP78 was detected in high salinity(30).So we infer that GRP78 in S.paramamosain might participate in protein folding and the response to environmental stress.