Mutation in a calpain-like protease affects the posttranslational mannosylation of phosphatases in Aspergillus nidulans

In this communication, we show that the palB7 mutation drastically reduced the mannose and N-acetylgalactosamine content of the pacA-encoded acid phosphatase secreted by the fungus Aspergillus nidulans at pH 5.0, compared to a control strain. By using mRNA differential display reverse transcription and polymerase chain reaction, we isolated two cDNAs from the control pabaA1 strain that were not detected in the palB7 mutant strain that encode a mannosyl transferase and a NADH-ubiquinone oxidoreductase. Thus, a defect in the posttranslational mannosylation of proteins could be the consequence of mutations in the palB gene, which encodes for a nuclear calpain-like protease that may have specific functions in the processing of transcription factor(s) similar to its homolog, RIM13, in Saccharomyces cereviseae.