Characterisation and comparative analysis of hydrophobin isolated from Pleurotus floridanus (PfH)

Hydrophobins are a class of small cysteine rich surface active proteins produced exclusively by filamentous fungi. It forms a nano layer in the cell-water interface, thereby protecting the emerging fungal hyphae from surrounding water. Even though hydrophobins have similar functions in fungi, they share less sequence similarity. In the current study, we made a comparative study of the hydrophobin produced by the mushroom Pleurotus floridanus (PfH). Mushroom P. floridanus was cultured in PD broth. The hydrophobin was purified by foam fractionation and characterized in terms of molecular weight, solubility and glycosylation. In the RP-HPLC analysis, the hydrophobin eluted at a retention time of 45.56 min. The molecular weight of the PfH was found to be 13.52 kDa by MALDI-TOF MS and the LC-MS/MS showed no similar sequence in MASCOT database. The hydrophobin gene of P. floridanus was amplified using custom-designed primers and the BLAST analysis showed 80% sequence similarity with the Vmh2-1 gene of Pleurotus ostreatus. The sequence was translated into protein using ExPASy, secondary and tertiary structure predictions were carried out using Jpred4 and Phyre2. The tertiary structure showed 91.5% similarity with the HYD1 hydrophobin of Schizophyllum commune. A comparative study of PfH with Vmh2-1 and HYD1 was performed using bioinformatics tools. Hydrophobic cluster analysis revealed that three of these proteins have uniformity in terms of amphiphilic and non-amphiphilic α-helices, whereas PfH has a unique proline clustering. Physicochemical analysis by ProtParam revealed that PfH shares similar properties with HYD1 and Vmh2-1, which can be correlated with its function.