Characterisation of CwpA, a putative glycosylphosphatidylinositolanchored cell wall mannoprotein in the Wlamentous fungus Aspergillus niger

Glycosylphosphatidylinositol (GPI)-anchored proteins in fungi are found at the cell surface, either as plasma membrane proteins (GPI-PMPs)or attached by a remnant of the GPI-anchor to the cell wall (GPI-CWPs). GPI-CWPs can be extracted from the cell wall by treatment with hydroXuoric acid (HF), which cleaves the phosphodiester bond that is present in the remnant of the GPIanchor. The Wlamentous fungus Aspergillus niger contains at least seven HF-extractable cell wall mannoproteins. One gene encoding an HF-extractable cell wall mannoprotein, cwpA, was cloned and further characterised. The protein sequence of CwpA indicated the presence of two hydrophobic signal sequences both at the N-terminus and C-terminus of the protein, for entering the ER and the addition of a GPI-anchor, respectively. A CwpA-speciWc antiserum was raised and in combination with fractionation experiments, we show that this protein was abundantly present as an HF-extractable protein in the cell wall of A. niger. ÆÉ 2005 Elsevier Inc. All rights reserved.