Cloning and characterization of two novel genes from Aspergillus niger encoding peptidyl prolyl cis-trans isomerases belonging to the cyclophilin family.

Patrick M.F. Derkx, Susan M. Madrid.


Aspergillus, a filamentous fungus, is widely used for the production of homologous and heterologous proteins but, compared to homologous proteins the production levels of heterologous proteins are usually low. Low levels of secreted proteins may be due to limitations at the post translational level. Peptidyl prolyl cis-trans isomerase (PPI) is a foldase which catalyzes the cis-transisomerization of peptide bonds preceding proline residues. Two A. niger genes encoding cyclophilin like PPIs have recently been cloned by heterologous screening of genomic and cDNA libraries. These genes encode a protein of approx. 20 kDa in size and both proteins contain a PPI specific catalytic core domain and a region involved in the binding of cyclosporin A. The CYPA protein, lacking signal sequence and ER retention signal, is most likely targeted to the cytosol. The CYPB protein however, contains a signal sequence and an ER retention signal which is responsible for targeting and retention of proteins in the ER. Transcription of cypB was shown to be induced by stress caused by unfolded proteins and heat shock whereas the transcription of cypA only increases moderately after heat shock. It is therefore likely that CYPB plays an important role in the folding of secretory proteins. Acknowledgments This work was funded by an EC Biotechnology program grant BI02 CT-942045

abstract No: 

Fungal Genet. Newsl. 46 (Supl):

Full conference title: 

Fungal Genetics Conference 20th
    • Fungal Genetics Conference 20th (1999)