Beta-tubulin carrying phenylalanine at position 200: molecular mechanisms & dependencies

How nutrients influence it

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Human evidence only

How nutrients reach it in more than one step

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What it does

Every recorded relationship this component is part of, grouped by its role. Plain wording comes first; the technical statement follows.

Recorded relationships

What acts on it

Albendazole-resistant Giardia lines showed major chromosome rearrangements and differences in the cytoskeleton, particularly the median body, implicating the cytoskeleton in the mechanism of resistance, but sequence data spanning the region encoding phenylalanine at position 200 demonstrated that the beta-tubulin gene did not carry a mutation at that codon, suggesting that phenylalanine at position 200 is not necessary for benzimidazole resistance.
Resistance to benzimidazole anthelmintics → Beta-tubulin carrying phenylalanine at position 200 source_derived_draftungraded
Experimental context and source evidence
evidence_span
{"source_cache": "artifacts/mebendazole-research/9158790.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "b1e25da8738886a9f416bb8411755eca925e232495786f938ef8f9afac40de30", "start_char": 0, "end_char": 1295, "text_sha256": "b1e25da8738886a9f416bb8411755eca925e232495786f938ef8f9afac40de30"}
experimental_model
Albendazole resistance induced in three Giardia cultures by stepwise drug exposure, with beta-tubulin sequencing
exposure
Growth in successively increasing albendazole, with immunofluorescence and PCR across codon 200
limitations
A counterexample obtained with albendazole rather than mebendazole, in a protozoan rather than a nematode. It is recorded because it tests the codon-200 rule directly and the rule fails.
nutrient_topic
Mebendazole research collection; topical membership is not evidence of a direct clinical effect, and mebendazole is recorded separately from albendazole, from the benzimidazole class and from its own crystal forms. · Mebendazole
organism
Giardia
plain_language
Resistant parasites that never touched the famous mutation, so it cannot be the only route.
primary_references
[mbz-p9158790] Albendazole resistance in Giardia is correlated with cytoskeletal changes but not with a mutation at amino acid 200 in beta-tubulin. (1996). https://pubmed.ncbi.nlm.nih.gov/9158790/ DOI: 10.1089/mdr.1996.2.303
tissue_or_cell_type
Cytoskeleton and beta-tubulin gene
Mebendazole: the tubulin it binds, why that is selective, the crystal form that decides whether any of it works, and the off-target that became an oncology programme (2026-09-22) · lines 277–288
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Albendazole resistance induced in three Giardia cultures by stepwise drug exposure, with beta-tubulin sequencing · source_derived_draft · unverified_draft
### mbz-resistance-without-codon-200 Albendazole-resistant Giardia lines showed major chromosome rearrangements and differences in the cytoskeleton, particularly the median body, implicating the cytoskeleton in the mechanism of resistance, but sequence data spanning the region encoding phenylalanine at position 200 demonstrated that the beta-tubulin gene did not carry a mutation at that codon, suggesting that phenylalanine at position 200 is not necessary for benzimidazole resistance. Condition category: normal nutrient_topic: Mebendazole research collection; topical membership is not evidence of a direct clinical effect, and mebendazole is recorded separately from albendazole, from the benzimidazole class and from its own crystal forms. plain_language: Resistant parasites that never touched the famous mutation, so it cannot be the only route. organism: Giardia tissue_or_cell_type: Cytoskeleton and beta-tubulin gene experimental_model: Albendazole resistance induced in three Giardia cultures by stepwise drug exposure, with beta-tubulin sequencing limitations: A counterexample obtained with albendazole rather than mebendazole, in a protozoan rather than a nematode. It is recorded because it tests the codon-200 rule directly and the rule fails. exposure: Growth in successively increasing albendazole, with immunofluorescence and PCR across codon 200 evidence_span: {"source_cache": "artifacts/mebendazole-research/9158790.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "b1e25da8738886a9f416bb8411755eca925e232495786f938ef8f9afac40de30", "start_char": 0, "end_char": 1295, "text_sha256": "b1e25da8738886a9f416bb8411755eca925e232495786f938ef8f9afac40de30"} [mbz-p9158790] Albendazole resistance in Giardia is correlated with cytoskeletal changes but not with a mutation at amino acid 200 in beta-tubulin. (1996). https://pubmed.ncbi.nlm.nih.gov/9158790/ DOI: 10.1089/mdr.1996.2.303
Complete structured claim and evidence

Where it participates (unsigned role)

All Haemonchus contortus tub-1 constructs encoding phenylalanine at position 200 conferred susceptibility to thiabendazole in benzimidazole-resistant Caenorhabditis elegans ben-1 mutants, whereas constructs carrying tyrosine at position 200 did not alter the resistant phenotype, leading to the conclusion that the single phenylalanine to tyrosine mutation at position 200 in beta-tubulin isotype 1 is the cause of benzimidazole resistance in Haemonchus contortus.
Beta-tubulin carrying tyrosine at position 200 → Resistance to benzimidazole anthelmintics source_derived_draftungraded
Experimental context and source evidence
availability_state
machinery_impairment Imported condition classification; unverified.
evidence_span
{"source_cache": "artifacts/mebendazole-research/7877171.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "091ba3ac445b68112bac29dec56d0d1a48e0d258714ebdbe090b5e7728e6ceaa", "start_char": 0, "end_char": 1532, "text_sha256": "091ba3ac445b68112bac29dec56d0d1a48e0d258714ebdbe090b5e7728e6ceaa"}
experimental_model
Heterologous expression of Haemonchus contortus beta-tubulin alleles in Caenorhabditis elegans ben-1 mutants
exposure
Parasite benzimidazole-sensitive and resistant alleles and in vitro mutagenised constructs, assayed with benomyl and thiabendazole
limitations
A functional test rather than an association: the alleles were put into a resistant host and the phenotype followed the codon. The assay drugs were benomyl and thiabendazole rather than mebendazole.
nutrient_topic
Mebendazole research collection; topical membership is not evidence of a direct clinical effect, and mebendazole is recorded separately from albendazole, from the benzimidazole class and from its own crystal forms. · Mebendazole
organism
Nematode
plain_language
Swapping one amino acid back made resistant worms susceptible again, which makes it the cause and not a coincidence.
primary_references
[mbz-p7877171] Beta-tubulin genes from the parasitic nematode Haemonchus contortus modulate drug resistance in Caenorhabditis elegans. (1995). https://pubmed.ncbi.nlm.nih.gov/7877171/ DOI: 10.1006/jmbi.1994.0102
tissue_or_cell_type
Beta-tubulin isotype 1
trigger_kind
machinery_impairment Imported condition classification; unverified.
Mebendazole: the tubulin it binds, why that is selective, the crystal form that decides whether any of it works, and the off-target that became an oncology programme (2026-09-22) · lines 264–275
AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text. · supports · Heterologous expression of Haemonchus contortus beta-tubulin alleles in Caenorhabditis elegans ben-1 mutants · source_derived_draft · unverified_draft
### mbz-phe200-causes-resistance All Haemonchus contortus tub-1 constructs encoding phenylalanine at position 200 conferred susceptibility to thiabendazole in benzimidazole-resistant Caenorhabditis elegans ben-1 mutants, whereas constructs carrying tyrosine at position 200 did not alter the resistant phenotype, leading to the conclusion that the single phenylalanine to tyrosine mutation at position 200 in beta-tubulin isotype 1 is the cause of benzimidazole resistance in Haemonchus contortus. Condition category: machinery_impairment nutrient_topic: Mebendazole research collection; topical membership is not evidence of a direct clinical effect, and mebendazole is recorded separately from albendazole, from the benzimidazole class and from its own crystal forms. plain_language: Swapping one amino acid back made resistant worms susceptible again, which makes it the cause and not a coincidence. organism: Nematode tissue_or_cell_type: Beta-tubulin isotype 1 experimental_model: Heterologous expression of Haemonchus contortus beta-tubulin alleles in Caenorhabditis elegans ben-1 mutants limitations: A functional test rather than an association: the alleles were put into a resistant host and the phenotype followed the codon. The assay drugs were benomyl and thiabendazole rather than mebendazole. exposure: Parasite benzimidazole-sensitive and resistant alleles and in vitro mutagenised constructs, assayed with benomyl and thiabendazole evidence_span: {"source_cache": "artifacts/mebendazole-research/7877171.abstract.txt", "locator": "Indexed abstract; zero-based, end-exclusive Unicode character offsets", "file_sha256": "091ba3ac445b68112bac29dec56d0d1a48e0d258714ebdbe090b5e7728e6ceaa", "start_char": 0, "end_char": 1532, "text_sha256": "091ba3ac445b68112bac29dec56d0d1a48e0d258714ebdbe090b5e7728e6ceaa"} [mbz-p7877171] Beta-tubulin genes from the parasitic nematode Haemonchus contortus modulate drug resistance in Caenorhabditis elegans. (1995). https://pubmed.ncbi.nlm.nih.gov/7877171/ DOI: 10.1006/jmbi.1994.0102
Complete structured claim and evidence

The events it takes part in

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Situations it appears in

Low-supply and faulty-machinery situations recorded in the chapters where this component plays a part.

In the sources

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Open hypotheses

Proposed ideas that involve this component. They are labeled as hypotheses and do not change any recorded statement.

This is a research prototype built from draft material. It is not medical advice, and its statements still await verification against the original studies.

Beta-tubulin carrying phenylalanine at position 200