Linkages of Ywp1 to other components of the Yarrowia lipolytica mycelial cell wall were studied by extraction with beta-mercaptoethanol and zymolyase (a beta-glucanase complex) and by the use of rabbit polyclonal antibody preparation raised against Ywp1. Ywp1 complexed with an N-glycosylated cell wall protein(s) to form supramolecular complexes through disulphide bridges (extractable with beta-mercaptoethanol) or bonded to beta-1,3-glucan (extractable with zymolyase). The lack of a specific morphological phenotype when YWP1 was knocked out by gene disruption might indicate that other proteins present in the cell wall of Y. lipolytica compensated for its loss. In this mutant, the electrophoretic pattern of proteins, detected with polyclonal antibodies against the entire cell wall, was different from that obtained with the parental strain, but sensitivity to calcofluor white, zymolyase and chitinase did not change. Quantitative analysis of fluorescence emitted by cells in the presence of fluorescent wheat germ agglutinin (FITC-WGA) indicated that chitin was organized in the cell wall of the mutant cells in a form different from that in the parental strain.