PreprintCited by 5Genomics and Phylogenetic StudiesMachine Learning in BioinformaticsFractal and DNA sequence analysis

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Protein Embeddings and Local Alignments

Open access
Malec, Julia, Golding, G. Brian, Ilie, Lucian·2025·Computational and Structural Biotechnology Journal

Preprint — published as 10.1016/j.csbj.2025.12.002 · Paper page

Abstract

Background: The advent of protein embeddings has revolutionized bioinformatics by providing contextual representations that capture functional and evolutionary patterns. They have become, alongside sequence alignments, the cornerstone of bioinformatics. While embeddings cannot replace alignments, they can greatly help improving their quality. Our goal is replacing the BLOSUM matrices, the decades-old standard scoring system for protein alignment, with an embedding-based scoring method. Results: We introduce a new scoring function and algorithm for local alignment of protein sequences, we offer a new comprehensive framework for evaluating local alignments. The score between two residues is given by the cosine similarity of their Ankh-embedding vectors and the algorithm uses dynamic programming with affine penalty. For the evaluation, we built multiple datasets, using both natural and inserted sequences, from the Conserved Domain Database, BAL-iBASE, and GPCRdb, designed a new algorithm for local alignment extraction, localization and quality evaluation, and employed five distance metrics to evaluate the similarity with the true alignment. We performed nearly one and a half million tests to compare the new algorithm with the best BLOSUM matrices, specialized GPCRtm matrices, and top programs, such as PEbA, ProtT5-score, DEDAL, vcMSA and pLM-BLAST. Regarding the protein embedding models, Ankh not only surpasses the best combination of ProtT5 and ESM2, but appears to better understand the “language” of proteins, as it behaves much better on natural sequences compared to artificial ones obtained by inserting domains in random protein sequences. Also, while ProtT5 and ESM2 combine to produce better results, Ankh does not combine well with other embeddings. Conclusions: The new Ankh-score-based program is vastly superior to the BLOSUM matrices and clearly superior to all existing methods. New light shed on the protein embeddings can guide future improvements. In order to facilitate the use of the new method and protocol, they are freely available as a web server at e-score.csd.uwo.ca and as source code at github.com/lucian-ilie/E-score .

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Graphical abstract
Graphical abstract CC BY-NC-ND · PubMed Central
Fig. 1 Alignment overhangs. Average lengths of the alignment overhangs for the CDD natural dataset are given for all BLOSUM matrices and several shift values of Ankh-score.
Fig. 1 Alignment overhangs. Average lengths of the alignment overhangs for the CDD natural dataset are given for all BLOSUM matrices and several shift values of Ankh-score.CC BY-NC-ND · PubMed Central
Fig. 2 Gap penalty sensitivity analysis. The performance of the Ankh-score is evaluated for sensitivity to gap penalty perturbation for the domain CD00012 and dcc distance in terms of (i) variation of the distance to the reference alignment, (ii) winning percentage of Ankh vs ProtT5 and (iii) winning percentage of Ankh vs best BLOSUM.
Fig. 2 Gap penalty sensitivity analysis. The performance of the Ankh-score is evaluated for sensitivity to gap penalty perturbation for the domain CD00012 and dcc distance in terms of (i) variation of the distance to the reference alignment, (ii) winning percentage of Ankh vs ProtT5 and (iii) winning percentage of Ankh vs best BLOSUM.CC BY-NC-ND · PubMed Central
Fig. 3 Missed alignments. Average percentage of the alignments missed by each scoring method on the CDD natural dataset. For pLM-BLAST we tested several values (100, 60, 20) for the minimum alignment parameter, attempting to reduce the amount of alignments missed.
Fig. 3 Missed alignments. Average percentage of the alignments missed by each scoring method on the CDD natural dataset. For pLM-BLAST we tested several values (100, 60, 20) for the minimum alignment parameter, attempting to reduce the amount of alignments missed.CC BY-NC-ND · PubMed Central
Fig. 4 Score examples. Ankh-scores (left column) and BLOSUM scores (right column) are given for two examples, a natural one (top row) and an insert one (bottom row).
Fig. 4 Score examples. Ankh-scores (left column) and BLOSUM scores (right column) are given for two examples, a natural one (top row) and an insert one (bottom row).CC BY-NC-ND · PubMed Central
Fig. 5 Ankh-score vs best BLOSUM. The plots are arranged with one row for each natural dataset and one column for each distance. In each plot, a test is plotted as a dot with coordinates giving the distances corresponding to the programs being compared: Ankh-score vs the best BLOSUM matrix. The dot is coloured blue if the first program wins and red otherwise. The legend gives the number of tests won by each program. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 5 Ankh-score vs best BLOSUM. The plots are arranged with one row for each natural dataset and one column for each distance. In each plot, a test is plotted as a dot with coordinates giving the distances corresponding to the programs being compared: Ankh-score vs the best BLOSUM matrix. The dot is coloured blue if the first program wins and red otherwise. The legend gives the number of tests won by each program. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)CC BY-NC-ND · PubMed Central
Fig. 6 Summary plot of overall comparison: (i) natural datasets (ii) insert datasets. The bar charts show the number of domain won by each method in the comparisons performed.
Fig. 6 Summary plot of overall comparison: (i) natural datasets (ii) insert datasets. The bar charts show the number of domain won by each method in the comparisons performed.CC BY-NC-ND · PubMed Central
Fig. 7 Wins percentage over identity level. The plots show the percentage of wins of Ankh-score vs best BLOSUM (top row), ProtT5-score (middle row) and ProstT5-score (bottom row), for natural (left), insert (middle), and all data (right). Two curves are given for each of the five distances, one solid curve for Ankh-score and a dotted of the same colour for the competitor. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
Fig. 7 Wins percentage over identity level. The plots show the percentage of wins of Ankh-score vs best BLOSUM (top row), ProtT5-score (middle row) and ProstT5-score (bottom row), for natural (left), insert (middle), and all data (right). Two curves are given for each of the five distances, one solid curve for Ankh-score and a dotted of the same colour for the competitor. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)CC BY-NC-ND · PubMed Central
Fig. 8 Distance ratio over identity level. The plots show the distance ratio, for all five distance, between Ankh-score vs best BLOSUM (top row), ProtT5-score (middle row) and ProstT5-score (bottom row), for natural (left), insert (middle), and all data (right). Ratio higher than 1 means Ankh-score is better than the competitor.
Fig. 8 Distance ratio over identity level. The plots show the distance ratio, for all five distance, between Ankh-score vs best BLOSUM (top row), ProtT5-score (middle row) and ProstT5-score (bottom row), for natural (left), insert (middle), and all data (right). Ratio higher than 1 means Ankh-score is better than the competitor.CC BY-NC-ND · PubMed Central

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Citations

Cites

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Metadata

Authors
Malec, J., Golding, G. B., & Ilie, L.
Affiliations
  • Western University (CA)
  • McMaster University (CA)
Corresponding author
Ilie, Lucian
Venue
Computational and Structural Biotechnology Journal
Publisher
openRxiv
Published
2025-07-27
Volume
31
Pages
24-37
ISSN
2001-0370 (ISSN-L)
OpenAlex
W4417105621
Cited by
5
References
1
Citations by year
2026: 5
FWCI
1.50
Type
journal article
Language
en
Open access
Locations
  • Computational and Structural Biotechnology Journal (publishedVersion, cc-by-nc-nd)
  • bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
  • PubMed Central (publishedVersion, cc-by-nc-nd)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
Funders
Natural Sciences and Engineering Research Council (RGPIN 2021-03978, RGPIN-2020-05733)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Genomics and Phylogenetic Studies
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Machine Learning in Bioinformatics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Fractal and DNA sequence analysis
Keywords
protein embeddings, local alignment, protein language models, BAliBASE, GPCRdb

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