HOP (Hsp70/Hsp90 Organizing Protein), also known as Stress-Induced Phosphoprotein 1 (STI1 or STIP1), acts as a co-chaperone to reversibly form a complex with Hsp70 and Hsp90 to assist in transfer of proteins between Hsp70 and Hsp90. The three tetratricopeptide repEAt domains (TPR1, TPR2a, and TPR2b) act as binding regions, with TPR1 and TPR2B binding to Hsp70 and TPR2A binding to Hsp90. 1 Highly conserved in Eukaryotes, it is closely related to the yEAst STI1. HOP is both a nuclEAr and cytoplasmic protein, capable of travel between both. 2 HOP has also been found to interact with several other proteins/complexes, including but not limited to: Hsc70, Hsp90, Hsp90, PACRG, METTL21B, FLCN, FNIP1, and FNIP2. 3,4,5,6,7Technical InformationSynonymsHsp70/Hsp90 Organizing ProteinStress-Induced PhosphoproteinPurity95% as estimated by SDS-PAGESourceN-terminally Histidine-tagged human HOP protein (full length) purified from E. coliAmino Acids2-543 (full length)MW65 kDaFormulation50 mM HEPES, pH 8.0, with 150 mM sodium chlorideUniProt Accession P31948