iva.pichova@uochb.cas.cz
Pathogenic yeasts of the genus Candida represent the most prevalent cause of mycotic diseases worldwide. They behave as opportunistic pathogens, which means that they can live in human hosts as harmless commensals, being kept under the control by the host immune system. One of the key survival strategies of fungal pathogens is the ability to proliferate in different carbon dioxide (CO2) concentrations. CO2 is among the most important gases for living organisms. In nature, the concentration of CO2 is balanced by an interconversion to hydrogen carbonate (HCO3, bicarbonate through the spontaneous reaction CO2 + H2O = HCO3- +H+). Its average amount required by organism is much greater than the amount produced spontaneously from CO2, bicarbonate production requires fine tuned regulation. For this reason, a highly diverse family of enzymes has evolved that are able to accelerate the interconversion reaction up to 10 000-fold. The members of this family, carbonic anhydrases (CAs), are able to catalyze reversible hydration of CO2 to give a HCO3- +H+ . CAs evolved in all three domains of life, and are divided into eight, evolutionarily unrelated classes (α, β, γ, δ, ζ, η, θ and ι) that independently arose from different precursors during convergent evolution. ß-CAs are present in many pathogenic microorganisms but not in the mammalian hosts and therefore represent possible target for drug development.
We determined the crystal structure of CA form Candida parapsilosis at 2.6 Å resolution. It assembles as a tetramer, with the active site located at the interface between two monomers. At the bottom of the substrate pocket, a zinc ion is coordinated by the three highly conserved residues Cys76, His131 and Cys134 in addition to a water molecule. Activity assays of full length and truncated versions of CpNce103 indicated that the N-terminal arm is indispensable for enzymatic activity and crystal packing.
The project National Institute of virology and bacteriology (Programme EXCELES, ID Project No. LX22NPO5103) - Funded by the European Union - Next Generation EU