Thus, iron induced flocculation and ROS accumulation were not related to each other. MCFO expression was see more induced by low iron levels The expression of genes involved in iron uptake is regulated by iron availability. HAIU genes are induced under restricted iron conditions and repressed under high iron concentrations [23]. As mentioned above, members of the corresponding protein families are present in the plasma membrane of C. albicans. Heating whole microbial cells resuspended in phosphate buffers to elevated temperatures was already described as a method for the extraction of proteins associated with the cell wall or with the plasma membrane of different microorganisms [40–42].

We applied a similar approach by briefly boiling C. albicans cells grown in YPD medium or RIM. Proteins involved in HAIU were expected to be more abundant in cells cultivated in RIM compared to YPD. Extracted proteins were separated by SDS PAGE and visualized by coomassie staining. A protein band (80–100 kDa), which was significantly accumulated in RIM (Figure 3A), Danusertib was analyzed by MALDI-TOF MS, MS/MS and N-terminal Edman degradation for identification. N-terminal sequencing of the protein extracted from the respective gel band resulted in the identification of the amino acid sequence KTHTxYYKTGxVNAN (amino acids given in the single letter code) which corresponds

to the N-terminal sequence of the MCFO Fet3p (KTHTWYYKTGWVNAN) after cleavage of a predicted 20 amino acid signal peptide (Figure 3B). In the genome of C. albicans, five MCFO encoding genes are present. These are FET3 (orf19.4211), FET31 (orf19.4213), FET33 (orf19.943), FET34 (orf19.4215) and FET99 (orf19.4212). The K21 residue is unique

for Fet3p among C. albicans MCFOs (Figure 3B). Additionally, a glutamic acid peak appeared at residue 21, but was less intense than the lysine peak. This is indicative for the MCFOs Fet31p, Fet34p and Fet99p (Figure 3B). MALDI-TOF MS-analysis led to the identification of three peptide peaks specific for Fet34p and two peaks specific for Fet3p in addition to one peak shared between Fet34p and Fet3p, another peak shared between Fet3p, Fet31p and one peak shared between Fet3p, Thalidomide Fet31p and Fet99p (Table 1). MS-MS analysis of the peak appearing at 1384.7 m/z unequivocally confirmed the selleck chemical presence of Fet34p in the excised band. Taken together, these data indicated the presence of at least Fet3p and Fet34p in the protein extract. However, presence of Fet31p and Fet99p is also possible and could neither be confirmed nor excluded. In general, all C. albicans MCFOs apart from Fet33p, are highly conserved among each other as Fet31p, Fet34p and Fet99p have an amino acid sequence identity ranging between 75 – 83% compared to Fet3p [15]. Figure 3 MCFOs expression was regulated by iron levels. (A) SDS-PAGE analysis of proteins extracted by heating whole yeast cells of C. albicans SC5314.