Publication Date:
2015-08-28
Description:
Calnexin (CNX), known as a lectin chaperone located in the endoplasmic reticulum (ER), specifically recognizes G 1 M 9 GN 2 -proteins and facilitates their proper folding with the assistance of ERp57 in mammalian cells. However, it has been left unidentified how CNX works in Aspergillus oryzae , which is a filamentous fungus widely exploited in biotechnology. In this study, we found that a protein disulfide isomerase homolog TigA can bind with A. oryzae CNX (AoCNX), which was revealed to specifically recognize monoglucosylated glycans, similarly to CNX derived from other species, and accelerate the folding of G 1 M 9 GN 2 -ribonuclease (RNase) in vitro. For refolding experiments, a homogeneous monoglucosylated high-mannose-type glycoprotein G 1 M 9 GN 2 -RNase was chemoenzymatically synthesized from G 1 M 9 GN-oxazoline and GN-RNase. Denatured G 1 M 9 GN 2 -RNase was refolded with highest efficiency in the presence of both soluble form of AoCNX and TigA. TigA contains two thioredoxin domains with CGHC motif, mutation analysis of which revealed that the one in N-terminal regions is involved in binding to AoCNX, while the other in catalyzing protein refolding. The results suggested that in glycoprotein folding process of A. oryzae , TigA plays a similar role as ERp57 in mammalian cells, as a partner protein of AoCNX.
Print ISSN:
0959-6658
Electronic ISSN:
1460-2423
Topics:
Biology
,
Medicine
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