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Calnexin overexpression increases manganese peroxidase production in Aspergillus niger

Author: Conesa, A. · Jeenes, D. · Archer, D.B. · Hondel, C.A.M.J.J. van den · Punt, P.J.
Institution: TNO Voeding
Source:Applied and Environmental Microbiology, 2, 68, 846-851
Identifier: 236457
doi: doi:10.1128/AEM.68.2.846-851.2002
Keywords: Biology · Biotechnology · Biosynthesis · Fungi · Genes · Manganese · Proteins · Binding protein · Microbiology · Calnexin · Fungal protein · Manganese peroxidase · Peroxidase · Aspergillus niger · Basidiomycetes · Bipa gene · Clxa gene · Controlled study · gene overexpression · Phanerochaete · Protein analysis · Protein expression · Aspergillus niger · Calcium-Binding Proteins · Calnexin · Culture Media · Fungal Proteins · Heme · HSP70 Heat-Shock Proteins · Peroxidases · Phanerochaete · Transformation, Genetic · Aspergillus · Aspergillus niger · Basidiomycota · Chrysosporium · Phanerochaete · Phanerochaete chrysosporium


Heme-containing peroxidases from white rot basidiomycetes, in contrast to most proteins of fungal origin, are poorly produced in industrial filamentous fungal strains. Factors limiting peroxidase production are believed to operate at the posttranslational level. In particular, insufficient availability of the prosthetic group which is required for peroxidase biosynthesis has been proposed to be an important bottleneck. In this work, we analyzed the role of two components of the secretion pathway, the chaperones calnexin and binding protein (BiP), in the production of a fungal peroxidase. Expression of the Phanerochaete chrysosporium manganese peroxidase (MnP) in Aspergillus niger resulted in an increase in the expression level of the cLxA and bipA genes. In a heme-supplemented medium, where MnP was shown to be overproduced to higher levels, induction of clxA and bipA was also higher. Overexpression of these two chaperones in an MnP-producing strain was analyzed for its effect on MnP production. Whereas bipA overexpression seriously reduced MnP production, overexpression of calnexin resulted in a four- to fivefold increase in the extracellular MnP levels. However, when additional heme was provided in the culture medium, calnexin overexpression had no synergistic effect on MnP production. The possible function of these two chaperones in MnP maturation and production is discussed. Chemicals/CAS: BipA protein, Aspergillus; Calcium-Binding Proteins; Calnexin, 139873-08-8; Culture Media; Fungal Proteins; Heme, 14875-96-8; HSP70 Heat-Shock Proteins; manganese peroxidase, EC; Peroxidases, EC 1.11.1.-