| Author |
Du W, Qi S, Zhen M, Liao M, Zhao Y, Ma J, Hao Y, Jiang H, Lu G, Liew CW, Chua N, Chen H, Hu G, Hemu X.
|
| Abstract |
Peptide asparaginyl ligases (PALs) are powerful tools for protein engineering but are limited by natural rarity and poor expression. We mine 23 cyclotide-rich Viola species, uncovering 29 PALs that expand the known repertoire to 47. A dual-objective screen identifies VdiPAL1 as the best-performed natural PAL, with twice efficiency of wt-VyPAL2 and 12 mg L-1 soluble expression in E. coli. A broad P2" specificity including Trp/Ile/Leu/Phe/Tyr/Met is discovered across diverse PALs, which enables sequential click-compatible liposome dual-functionalization. 1.8 Å crystal structure of VdiPAL1 reveals a pre-organized near-attack conformation (NAC), supported by constant-pH MD simulations linking pH-dependent reactivity to NAC geometry. Our homology- and structure-based design yields VyOpt1, a quintuple mutant of VyPAL2 with over 24-fold improved expression via enhanced cap-domain foldability in a single design-test cycle. This work expands the PAL family and demonstrates a transferable cap-domain-based engineering strategy, highlighting natural diversity as a powerful driver of enzyme discovery and optimization.
|
