Plasmid generation. The selected ancestors were designed with an in-phase N-terminal His-tag and cloned into pET28a using the restriction sites NdeI and XhoI. The sequences were codon optimised for E. coli and the plasmids were synthesised by Twist Biosciences (CA, USA). Site-directed mutagenesis was performed using the primers and conditions in Supplementary Tables and. The PCR mixture was treated with DpnI for 1 h at 37 °C, NEB-5α competent E. coli cells were transformed with 2 μL of the resulting treated DNA, in accordance with the manufacturer's instructions (New England Biolabs). The constructs and mutations were confirmed via DNA sequencing, carried out by Eurofins Genomics (Germany).