Table 1.
Summary of modules and their proposed functional roles
| Class | Nr | Module | Structure | Functions | Length (aa) |
|---|---|---|---|---|---|
| I | 1 | Protozyme | Molten globule | Amino acid activation (72,73) | 37−56 |
| 2 | Urzyme | 4 stranded Rossmann fold | tRNA aminoacylation (28) | 87−110* | |
| 3 | CP1 | Exoskeleton † | tRNA binding, dimerisation (76,102) | 43−73 | |
| 4 | LysRS-I | β rich domain (19) | 58−90 | ||
| 5 | Z | 3 antiparallel β-strands (77) | 16−51 | ||
| 6 | ArgRS | 3-5 helix bundle (77) | 37−113 | ||
| 7 | Ib | Loop flanked by two helices | Acceptor stem recognition (27) | 63−100 | |
| 8 | CysRS | Partially disordered lasso | tRNA binding (30) | 30−55 | |
| 9 | CP2 | 2 helix bundle | Amino acid activation and editing (78) | 30−39 | |
| 10 | ZF | Cysteine-rich zinc finger | tRNA aminoacylation (79,80) | 19−44 | |
| 11 | Editing I | Large globular domain | Post-transfer editing (61,62) | 172−318 | |
| 12 | LeuRS-A 1 | 2 helices (62) | 25−74 | ||
| 13 | LeuRS-A 2 | 4 helices (62) | 52−76 | ||
| 14 | CP3 | Cysteine-rich zinc finger (62) | 25−77 | ||
| 15 | LeuRS-B | Several β-strands, 2 helices (61) | 38−87 | ||
| II | 1 | Protozyme | Molten globule | Amino acid activation (72,73) | 35−50 |
| 2 | Urzyme | 3 stranded antiparallel fold | tRNA aminoacylation (28) | 73−88* | |
| 3 | 6 fold | 6 stranded antiparallel fold | 131−155 | ||
| 4 | AlaRS | Helical loop † | tRNA aminoacylation (83,103) | 30−40 | |
| 5 | SI | Loop | Aminoacylation, dimerisation (56–58) | 13−28 | |
| 6 | SepRS | Disordered / helical bundle (104) | 73−77 | ||
| 7 | HisRS | Disordered † | tRNA binding (105) | 92−128 | |
| 8 | PheRS-A | 2 helices (67) | 28−41 | ||
| 9 | IIb 1 | Loop flanked by two helices † | 43−80 | ||
| 10 | IIb 2 | 2 helix bundle | 24−46 | ||
| 11 | AspRS 1 | 6-stranded antiparallel fold | tRNA interactions (31) | 44−66 | |
| 12 | AspRS 2 | See above | 45−48 | ||
| 13 | SerRS-A | Helix-turn-helix | Dimerisation (63) | 36 | |
| 14 | IIa | β-hairpin | 6−18 | ||
| 15 | ThrRS | Helix-strand † | Amino acid activation (106) | 35−42 | |
| 16 | ProRS | β-hairpin followed by loop | 32−36 | ||
| 17 | Editing II | Large soluble domain | Post-transfer editing (66) | 147−173 | |
| 18 | GlyRS 1 | Zinc ribbon | tRNA aminoacylation (32) | 44−115 | |
| 19 | GlyRS 2 | 2 strands and 2−3 helices (32) † | 37−44 | ||
| 20 | GlyRS-E | Disordered | tRNA binding (32) | 86−94 |
Modules in bold font are ancestral catalytic domains, and those in standard font are insertions. Module length ranges are 95% credible intervals across all AlphaFold generated structures. †These elements contain a strand which runs parallel to the N-terminal edge of the Rossmann fold (Class I) or the C-terminal edge of the β-sheet (Class II). *Universal urzyme structures were constructed from aligned helices and strands, excluding loops, so these values underestimate the expected lengths (∼130 aa).