Two novel heat-soluble protein families abundantly expressed in an anhydrobiotic tardigrade
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Discovery of CAHS and SAHS protein families as heat-soluble, abundantly expressed proteins in the anhydrobiotic tardigrade R. varieornatus
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CAHS proteins contain characteristic 19-mer CAHS motifs
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Identified by mass spectrometry in heat-soluble proteome fraction
Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein
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R. varieornatus genome contains 16 CAHS genes and 13 SAHS genes
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CAHS and SAHS are constitutively and abundantly expressed during dehydration and rehydration with only minor transcriptional changes
"These abundantly expressed proteins included previously identified tardigrade-unique heat-soluble proteins, CAHS and SAHS, both of which maintain solubility even after heat treatment and are proposed to be involved in the protection of biomolecules during desiccation"
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CAHS proteins contain 2 repeats of 19-mer peptides designated as CAHS-motifs
Reconsidering the glass transition hypothesis of intrinsically unstructured CAHS proteins in desiccation tolerance of tardigrades
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CAHS proteins contribute to anhydrobiosis but specific mechanisms are not yet fully identified
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Protection during anhydrobiosis may occur via stabilization of vitrifying small molecules such as sugars rather than direct glass transition of CAHS proteins
Gene Ontology annotation based on UniProtKB/Swiss-Prot Subcellular Location vocabulary mapping, accompanied by conservative changes to GO terms applied by UniProt
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UniProt SUBCELLULAR LOCATION annotation for CAHS2 (J7MDG6) records cytoplasmic localization by similarity to CAHS1 (J7M3T1), which was experimentally localized by GFP-fusion in PMID:22937162. This mapping reference is used to convert the controlled-vocabulary subcellular location into the GO:0005737 (cytoplasm) annotation with IEA evidence.
Deep research synthesis on CAHS2 (J7MDG6) from R. varieornatus
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CAHS2 is best annotated as a non-enzymatic, cytosolic stress-protection IDP whose family contributes to anhydrobiosis tolerance via stress-responsive structural transitions (disorder to alpha-helix) and amphipathic helical shielding; no CAHS2-specific in vivo phenotype or interaction partners are yet reported.
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Two converging family-level mechanistic models for CAHS proteins are (i) stress-induced self-assembly into filamentous networks/gels that change cellular material properties, and (ii) stabilization of vitrifying small molecules during desiccation rather than direct glass-transition of the CAHS protein itself.