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9rkp

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Crystal structure of the coiled-coil based fibril core of the tardigrade CAHS-8 protein

Structural highlights

9rkp is a 2 chain structure with sequence from Hypsibius exemplaris. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	X-ray diffraction, Resolution 2.6Å
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

CAHS8_HYPEX CAHS proteins are cytosolic heat soluble proteins that seem to contribute to the anhydrobiosis in tardigrades, but their specific mechanisms are yet to be identified (PubMed:28306513, PubMed:33545053). It is possible that protection during anhydrobiosis might occur via the stabilization of vitrifying small molecules such as sugars, but not via the direct glass transition of CAHS proteins themselves (Probable).^[1] ^[2] ^[3]

Publication Abstract from PubMed

Cytosolic Abundant Heat-Soluble (CAHS) proteins are thought to be responsible for protection of tardigrades against conditions of extreme environmental stress, in particular desiccation. Hypsibius exemplaris CAHS-8 is intrinsically disordered in solution, undergoing conformational transformation as a function of stress, assembling into fibres that form a hydrogel. Here we present the crystal structure of the fibrils of CAHS-8, comprising a single 101 residue-long helix, forming an atypical 90 amino-acid coiled-coil dimer exhibiting non-canonical periodicities and assembling into fibrils via a second coiled coil interface associating adjacent dimers via the opposing face of the helix. Combination with electron microscopy, atomic force microscopy and disorder modelling provides structural insight into the details of this assembly that is essential for cell survival. Individual fibrils appear to interact in a pairwise manner, possibly via their intrinsically disordered tails, forming straight fibres.

Fibril Structure of Desiccation-Protective Tardigrade Protein CAHS-8.,Malki A, Teulon JM, Mikkola EA, Maurin D, Pellequer JL, Nanao MH, Blackledge M Angew Chem Int Ed Engl. 2025 Dec 31:e19912. doi: 10.1002/anie.202519912. PMID:41474256^[4]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.