Stch encodes the 'ATPase core' of a microsomal stress70 protein

Gregory A. Otterson, Gregory C. Flynn, Robert A. Kratzke, Amy Coxon, Patrick G. Johnston, Frederic J. Kaye

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


The stress70 protein chaperone family plays a central role in the processing of cytosolic and secretory proteins. We have cloned a human cDNA, designated Stch, that is conserved in rat tissues and which encodes a novel microsome-associated member of the stress70 protein chaperone family. Stch mRNA is constitutively expressed in all human cell types and is induced by incubation with the calcium ionophore A23187, but not by exposure to heat shock. Inspection of the predicted amino acid sequence reveals that the STCH product contains a unique hydrophobic leader sequence and shares homology within the amino terminal domains of the stress70 gene family, but has a 50 residue insertion within the ATP-binding domains and truncates the carboxyl terminal peptide-binding region. Immunofluorescent and subcellular analyses show that STCH migrates predominantly as a 60 kDa species and is enriched in a membrane-bound microsome fraction. In contrast to purified BiP and dnaK, however, STCH demonstrates ATPase activity that is independent of peptide stimulation. Stch, therefore, encodes a calcium-inducible, microsome-associated ATPase activity with properties similar to a proteolytically cleaved N-terminal HSC70/BiP fragment. This truncated stress70 molecule may allow increased diversity in cellular responses to protein processing requirements.

Original languageEnglish (US)
Pages (from-to)1216-1225
Number of pages10
JournalEMBO Journal
Issue number5
StatePublished - Mar 1 1994


  • ATPase
  • Microsome
  • Protein chaperone
  • Stress70
  • cDNA cloning


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