Identification of Candida albicans wall mannoproteins covalently linked by disulphide and/or alkali-sensitive bridges

This paper describes the results obtained by analysing the human pathogen Candida albicans cell wall subproteome by mass spectrometry, using extraction procedures aimed at releasing proteins bound by disulphide bridges (RAE-CWP) or alkali-labile ester linkages (ALS-CWP). Ten of the total proteins released from the wall by β-ME and/or NaOH contained a potential signal peptide, lacked a GPI cell wall hydrophobic C-terminal domain and were identified as true wall proteins by in silico analysis, whereas four additional proteins were identified as bound to the plasma membrane. The results surprisingly demonstrated that, in addition to the expected RAE-CWP and ALS-CWP proteins, 16 GPI proteins were bound to the wall by disulphide or alkali-sensitive bonds, since they were released by β-ME and/or NaOH. The biological significance of these results is discussed in relation to the added complexity of the organization of the proteins in the C. albicans cell wall.