The N-terminal hydrophobic domain of P450c21 is required for membrane insertion and enzyme stability

L. C. Hsu, M. C. Hu, H. C. Cheng, J. C. Lu, B. C. Chung

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


Microsomal cytochromes P-450 are known to be integrated into smooth endoplasmic reticulum through their hydrophobic sequences located at the N termini. The length requirement of the membrane insertion signal was determined by the generation of six plasmids encoding mutant P450c21 that lacked various portions of the N-terminal hydrophobic domains. When they were transcribed and translated in vitro in the presence of endoplasmic reticulum membranes, mutant protein lacking more than a third of the first hydrophobic domain gradually lost the ability to insert into the membrane and stayed mostly in the soluble fraction when the first N-terminal hydrophobic domain was removed. The steady-state amount of the truncated proteins was progressively reduced in parallel to the extent of their N-terminal deletions, due to their fast degradation. This process was accompanied by a decrease in the enzymatic activity. Therefore, the first hydrophobic domain of P450c21 not only serves as a membrane targeting and anchoring domain, but it is also important for the in vivo protein stability.

Original languageEnglish
Pages (from-to)14682-14686
Number of pages5
JournalJournal of Biological Chemistry
Issue number20
Publication statusPublished - 1993
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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