Evidence map›Paper›PMID 39074291›Full record

ArticleProceedings of the National Academy of Sciences of the United States of America2024

A combinatorially complete epistatic fitness landscape in an enzyme active site.

Kadina E Johnston, Patrick J Almhjell, Ella J Watkins-Dulaney, Grace Liu, Nicholas J Porter, Jason Yang, Frances H Arnold

Abstract read
In one paragraph

Article in Proceedings of the National Academy of Sciences of the United States of America, 2024. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 32 papers.

0numbers the graph read from it
0cells of the map it votes in
32citing papers in PubMed
–field-weighted citation impact
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

32 citing papers in PubMed.

  1. Review
  2. Phage-assisted continuous evolution of enzymes for noncanonical tyrosine biosynthesis.Proceedings of the National Academy of Sciences of the United States of America · 2026
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  12. Determinants of metal import and specificity in a bacterial transporter.bioRxiv : the preprint server for biology · 2026
    Article
  13. Review
  14. Article
  15. Deconstructing empirical fitness seascapes across scales of granularity.bioRxiv : the preprint server for biology · 2026
    Article
  16. Efficient, Few-shot Directed Evolution with Energy Rank Alignment.bioRxiv : the preprint server for biology · 2026
    Article
  17. Article
  18. Article
  19. Review
  20. Knowledgeable Language Models as Black-Box Optimizers for Personalized Medicine.... International Conference on Learning Representations · 2026
    Article
4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

7 authors.

Kadina E JohnstonDivision of Biology and Bioengineering, California Institute of Technology, Pasadena, CA 91125.ORCID 0000-0002-2214-3534
Patrick J Almhjell *Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125.ORCID 0000-0003-0977-841X
Ella J Watkins-Dulaney *Division of Biology and Bioengineering, California Institute of Technology, Pasadena, CA 91125.ORCID 0000-0002-0585-1598
Grace LiuDivision of Biology and Bioengineering, California Institute of Technology, Pasadena, CA 91125.
Nicholas J PorterDivision of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125.
Jason YangDivision of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125.ORCID 0000-0003-3184-1550
Frances H ArnoldDivision of Biology and Bioengineering, California Institute of Technology, Pasadena, CA 91125.ORCID 0000-0002-4027-364X

Funding

Amgen (Amgen Inc.) N/ACaltech AI4Science/Amazon AWS Fellowship N/ACaltech Center for Environmental Sciences N/AHelen Hay Whitney Foundation (HHWF) MerckNSF | National Science Foundation Graduate Research Fellowship Program (GRFP) N/AU.S. Department of Energy (DOE) DE-SC0022218
6 · The paper itself

Abstract

Protein engineering often targets binding pockets or active sites which are enriched in epistasis-nonadditive interactions between amino acid substitutions-and where the combined effects of multiple single substitutions are difficult to predict. Few existing sequence-fitness datasets capture epistasis at large scale, especially for enzyme catalysis, limiting the development and assessment of model-guided enzyme engineering approaches. We present here a combinatorially complete, 160,000-variant fitness landscape across four residues in the active site of an enzyme. Assaying the native reaction of a thermostable β-subunit of tryptophan synthase (TrpB) in a nonnative environment yielded a landscape characterized by significant epistasis and many local optima. These effects prevent simulated directed evolution approaches from efficiently reaching the global optimum. There is nonetheless wide variability in the effectiveness of different directed evolution approaches, which together provide experimental benchmarks for computational and machine learning workflows. The most-fit TrpB variants contain a substitution that is nearly absent in natural TrpB sequences-a result that conservation-based predictions would not capture. Thus, although fitness prediction using evolutionary data can enrich in more-active variants, these approaches struggle to identify and differentiate among the most-active variants, even for this near-native function. Overall, this work presents a large-scale testing ground for model-guided enzyme engineering and suggests that efficient navigation of epistatic fitness landscapes can be improved by advances in both machine learning and physical modeling.

Indexed as

Catalytic DomainEpistasis, GeneticTryptophan SynthaseAmino Acid SubstitutionModels, MolecularProtein EngineeringTryptophan Synthasebiocatalysisdirected evolutionepistasismachine learningtryptophan synthase

Identifiers

PMID39074291
PMCPMC11317637

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Registered trials

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.