Fig. 1

Alignment of A. wt Pab1 from C. cinerea monokaryon OK130 (CcPab1) with PabA (EcPabA, underlaid in yellow) and PabB of E. coli (EcPabB, underlaid in dusky pink) and B. wt Ade8 from C. cinerea strain AmutBmut (CcAde8) with PurD (EcPurD, underlaid in yellow) and PurM of E. coli (EcPurM, underlaid in dusky pink), respectively. a The catalytic triad, glutamine binding residues and residues involved in ammonia tunnel formation in PabA are marked with red, green and blue symbols *, respectively. Other residues affecting enzymatic activities and bonding to PabB are marked with grey squares. The position of a stabilizing residue stretch called oxyanion hole is underlaid in light blue, a sequence stretch for chorismate signal transfer in olive [29, 30, 75]. Red letters in PabB mark helical regions, blue letters β-sheets. The conserved PIKGT motif, sequences for interaction with PabA, for signal transfer of chorismate binding, and of a binding pocket for tryptophan implicated in structural stabilization are underlaid in olive, bright yellow, grey and light blue, respectively. The residue K in the PIKGT motif which is mutated in C. cinerea AmutBmut (K546E) is marked in red. Symbols * in red and black mark (predicted) active site residues and Mg²⁺-binding residues in two chorismate-interacting helices, respectively. Triangles in black indicate residues that contact the bound tryptophan and grey squares further residues where mutations affect functionality [28,29,30,31, 76]. b Red, blue, green and magenta letters mark the N, B, A, and C domains of PurD. The positions of the P-loop and the flexible A and B loops in PurD [56] are underlaid in light blue, olive and orange, respectively. Symbols * in black, red, and blue mark residues that recognize the adenine base, ribose and phosphate of the nucleotide, whereas grey squares indicate residues interacting with the ligand PRA [56, 57]. The residue N in the A loop which is mutated in C. cinerea OK130 (N231D) is marked in red. In PurM, symbols * mark (predicted) nucleotide binding residues and triangles (in grey predicted) binding sites of the substrate N-formylglycinamidine ribonucleotide (FGAM) [58]