Exploring hydrophilic sequence space to search for uncharted foldable proteins by AlphaFold2

Proteins typically fold into unique three-dimensional structures largely driven by interactions between hydrophobic amino acids. This understanding has helped improve our knowledge of protein folding. However, recent research has shown an exception to this idea, demonstrating that specific threonine...

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Main Authors: Naoki Tomita, Hiroki Onoda, Leonard M. G. Chavas, George Chikenji
Format: Article
Language:English
Published: The Biophysical Society of Japan 2025-03-01
Series:Biophysics and Physicobiology
Subjects:
Online Access:https://doi.org/10.2142/biophysico.bppb-v22.0005
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author Naoki Tomita
Hiroki Onoda
Leonard M. G. Chavas
George Chikenji
author_facet Naoki Tomita
Hiroki Onoda
Leonard M. G. Chavas
George Chikenji
author_sort Naoki Tomita
collection DOAJ
description Proteins typically fold into unique three-dimensional structures largely driven by interactions between hydrophobic amino acids. This understanding has helped improve our knowledge of protein folding. However, recent research has shown an exception to this idea, demonstrating that specific threonine-rich peptides have a strong tendency to form β-hairpin structures, even in the highly hydrophilic amino acid sequences. This finding suggests that the hydrophilic amino acid sequence space still leaves room for exploring foldable amino acid sequences. In this study, we conducted a systematic exploration of the repetitive amino acid sequence space by AlphaFold2 (AF2), with a focus on sequences composed exclusively of hydrophilic residues, to investigate their potential for adopting unique structures. As a result, the sequence space exploration suggested that several repetitive threonine-rich sequences adopt distinctive conformations and these conformational shapes can be influenced by the length of the sequence unit. Moreover, the analysis of structural dataset suggested that threonine contributes to the structural stabilization by forming non-polar atom packing that tolerates unsatisfied hydrogen bonds, and while also supporting other residues in forming hydrogen bonds. Our findings will broaden the horizons for the discovery of foldable amino acid sequences consisting solely of hydrophilic residues and help us clarify the unknown mechanisms of protein structural stabilization.
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publisher The Biophysical Society of Japan
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spelling doaj-art-e92e121624c542fba24a507080b080992025-08-20T02:03:06ZengThe Biophysical Society of JapanBiophysics and Physicobiology2189-47792025-03-012210.2142/biophysico.bppb-v22.0005Exploring hydrophilic sequence space to search for uncharted foldable proteins by AlphaFold2Naoki Tomita0Hiroki Onoda1Leonard M. G. Chavas2George Chikenji3Department of Applied Physics, Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8602, JapanNagoya University Synchrotron Radiation Research Center, Nagoya University, Nagoya, Aichi 464-8603, JapanDepartment of Applied Physics, Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8602, JapanDepartment of Applied Physics, Graduate School of Engineering, Nagoya University, Nagoya, Aichi 464-8602, JapanProteins typically fold into unique three-dimensional structures largely driven by interactions between hydrophobic amino acids. This understanding has helped improve our knowledge of protein folding. However, recent research has shown an exception to this idea, demonstrating that specific threonine-rich peptides have a strong tendency to form β-hairpin structures, even in the highly hydrophilic amino acid sequences. This finding suggests that the hydrophilic amino acid sequence space still leaves room for exploring foldable amino acid sequences. In this study, we conducted a systematic exploration of the repetitive amino acid sequence space by AlphaFold2 (AF2), with a focus on sequences composed exclusively of hydrophilic residues, to investigate their potential for adopting unique structures. As a result, the sequence space exploration suggested that several repetitive threonine-rich sequences adopt distinctive conformations and these conformational shapes can be influenced by the length of the sequence unit. Moreover, the analysis of structural dataset suggested that threonine contributes to the structural stabilization by forming non-polar atom packing that tolerates unsatisfied hydrogen bonds, and while also supporting other residues in forming hydrogen bonds. Our findings will broaden the horizons for the discovery of foldable amino acid sequences consisting solely of hydrophilic residues and help us clarify the unknown mechanisms of protein structural stabilization.https://doi.org/10.2142/biophysico.bppb-v22.0005threoninealphafold2hydrophilic amino acid sequence
spellingShingle Naoki Tomita
Hiroki Onoda
Leonard M. G. Chavas
George Chikenji
Exploring hydrophilic sequence space to search for uncharted foldable proteins by AlphaFold2
Biophysics and Physicobiology
threonine
alphafold2
hydrophilic amino acid sequence
title Exploring hydrophilic sequence space to search for uncharted foldable proteins by AlphaFold2
title_full Exploring hydrophilic sequence space to search for uncharted foldable proteins by AlphaFold2
title_fullStr Exploring hydrophilic sequence space to search for uncharted foldable proteins by AlphaFold2
title_full_unstemmed Exploring hydrophilic sequence space to search for uncharted foldable proteins by AlphaFold2
title_short Exploring hydrophilic sequence space to search for uncharted foldable proteins by AlphaFold2
title_sort exploring hydrophilic sequence space to search for uncharted foldable proteins by alphafold2
topic threonine
alphafold2
hydrophilic amino acid sequence
url https://doi.org/10.2142/biophysico.bppb-v22.0005
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