Identification
of cell wall proteins of the fungal pathogen Candida albicans and other fungi using
mass-spectrometric and genome-wide computational approaches.
Piet W.J. De Groot (1), Henk L. Dekker (2), Albert D. De Boer (1), Klaas J.
Hellingwerf (1), Chris G. De Koster (2), Frans M. Klis (1)
(1) Laboratory for Microbiology, University of Amsterdam, Nieuwe Achtergracht,
Amsterdam, 1018 WV, The Netherlands (pgroot@science.uva.nl); (2) Mass
Spectrometry Group, SILS-UvA, Amsterdam, The Netherlands
Candida albicansis the major cause of fungal diseases in humans. Its cell wall is the first point of contact with the host and is instrumental in the infection process. Adhesive and invasive properties of C. albicans cells are determined by cell wall proteins (CWPs) which therefore form a valuable source of potential virulence factors and antifungal drug targets. The cell wall of C. albicans contains two classes of cell wall proteins (CWPs), GPI-dependent CWPs and Pir-CWPs, which are covalently linked to the beta-glucan network. We have used two independent approaches for the identification of cell wall proteins. (1) A genome-wide bio-informatics approach. Using a motif that describes the C-terminal region of glycosylphosphatidylinositiol (GPI) anchored proteins, and also taking into account other sequence requirements for GPI-proteins, we have identified 106 putative GPI-proteins. This approach also proved to be effective in other fungi. In S. cerevisiae, S. pombe and N. crassa we identified 69, 33 and 97 putative GPI-proteins, respectively. (2) A mass-spectrometric approach to identify proteins from C. albicans cell wall extracts. CWPs were chemically released from SDS-resistant cell wall fractions and fractionated using anion-exchange chromatography. Protein bands obtained by SDS-PAGE were subjected to Q-TOF analysis. This has resulted in the identification of eight GPI-CWPs, that were all present in our set of predicted GPI-anchored proteins, and one Pir protein.