Molecular analysis of a glucose-regulated gene (grp78) of Neurospora crassa

The nucleotide sequence of the gene encoding the glucose-regulated protein 78 (GRP78) of Neurospora crassa was determined. The ORF codes for a protein of 662 amino acids (72 kDa) and belongs to the heat shock protein 70 (hsp70) gene family, which is characterized by three HSP70 'signature sequences'. The grp78 gene contains 5 introns. The protein carries the ER retention signal HDEL at its carboxy terminus and is most homologous to the KAR2/GRP78 protein of Saccharomyces cerevisiae (78%) and to KAR2/BiP of Yarrowia lipolytica (76%). The expression of grp78 is constitutive and can be enhanced by starvation, treatment with tunicamycin, the calcium ionophore A23187 or elevated temperatures (40 degrees C). An uninterrupted ORF was found on the reverse cDNA strand of grp78. The putative peptide shows 47% homology to the NAD-specific glutamate dehydrogenase of Achlya klebsiana.