The secondary structure of the analyzed variants was experimentally verified using circular dichroism (CD) spectroscopy. CD spectra were measured at 15°C using a spectropolarimeter Chirascan (Applied Photophysics). The samples were dissolved in 1 mM HEPES buffer or in the 50 mM Phosphate buffer and their concentration was adjusted to approximately 0.18 mg/ml. Data were collected from 185 to 260 nm with 0.25 s integration time and 1 nm bandwidth using a 0.1 cm quartz cuvette. Each spectrum was obtained as an average of five individual repeats. Prediction of CD spectra has been performed by the web tool PDBMD2CD (). For this prediction, either experimental structures from PDB database (1CQW for DhaA) or AlphaFold models were taken as input. The estimation of secondary structure elements from experimental data and PDB database structures (uploading own PDB files -AlphaFold modelswas unfortunately not available at the moment of data analysis) was performed additionally by the web tool BeStSel ().