9q8o
Crystal structure of Hsp82-MD in complex with the CS domain of Sgt1
Structural highlights
FunctionHSP82_YEAST Molecular chaperone that promotes the maturation, structural maintenance and proper regulation of specific target proteins involved in cell cycle control and signal transduction. Undergoes a functional cycle that is linked to its ATPase activity. The nucleotide-free form of the dimer is found in an open conformation in which the N-termini are not dimerized and the complex is ready for client protein binding. Binding of ATP induces large conformational changes, resulting in the formation of a ring-like closed structure in which the N-terminal domains associate intramolecularly with the middle domain and also dimerize with each other, stimulating their intrinsic ATPase activity and acting as a clamp on the substrate. Finally, ATP hydrolysis results in the release of the substrate. This cycle probably induces conformational changes in the client proteins, thereby causing their activation. Interacts dynamically with various co-chaperones that modulate its substrate recognition, ATPase cycle and chaperone function. Required for growth at high temperatures.[1] Publication Abstract from PubMedThe Hsp90 molecular chaperone system is regulated by numerous co-chaperones that modulate its function. In Saccharomyces cerevisiae, most of these cofactors can be deleted without affecting viability. Of the three essential ones, only the function of Sgt1 has remained enigmatic. Our in vivo and in vitro experiments define key structural elements and determine the essential function of Sgt1 in the chaperoning of client proteins. We demonstrate that yeast Sgt1 adopts a unique binding mode, engaging primarily with the middle domain of Hsp90. Through simultaneous interaction with both Hsp90 and client proteins, Sgt1 enhances client maturation efficiency. Specifically, Sgt1 stabilizes Hsp90-client complexes and prevents their dissociation by the co-chaperone Aha1. Our findings reveal a previously unrecognized layer of Hsp90 regulation, highlighting Sgt1 as a critical modulator of chaperone cycle progression. The essential co-chaperone Sgt1 regulates client dwell time in the Hsp90 chaperone cycle.,Engler S, Delhommel F, Dodt C, Lopez A, Faust O, Elimelech A, Napolitano V, Popowicz GM, Rosenzweig R, Sattler M, Buchner J Mol Cell. 2026 Jan 8;86(1):166-179.e6. doi: 10.1016/j.molcel.2025.12.002. Epub , 2025 Dec 22. PMID:41435837[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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