The role of the membrane domain in the regulated degradation of 3-hydroxy-3-methylglutaryl coenzyme a reductase

Kristin Chun, Robert D. Simoni

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

We have constructed a series of mutations in the membrane and linker domains of Syrian hamster 3-hydroxy-3-methylglutaryl-(HMG) CoA reductase in order to determine the regions critical for the regulated degradation of the enzyme. In transfected Chinese hamster ovary cells, we have expressed a fusion protein, HMGal, which consists of the membrane and linker domains of the Syrian hamster HMG-CoA reductase fused to β-galactosidase. Using this fusion protein, we have determined that a deletion of 64 amino acids from the central region of the membrane domain causes the protein to be degraded extremely rapidly. In addition, deletion of PEST sequences has little effect on degradation, but deletion of the linker domain makes the protein's degradation insensitive to sterols and mevalonate. In addition to deletion mutations, we have systematically replaced each hydrophobic, putative membrane spanning region of the membrane domain with the first transmembrane sequence from bacteriorhodopsin. Replacement of span 4 has no effect on degradation. Replacements of spans 5 or 6 result in a protein which has a normal basal rate of degradation, but this rate of degradation is not accelerated by mevaionate, low density lipoprotein, or 25-hydroxycholesterol. Replacement of span 3 results in a protein whose degradation is similarly not accelerated by sterols or mevalonte, but since this protein might be mislocalized, these results are inconclusive. Replacement of span 7 yields a short-lived protein which is degraded more rapidly in response to mevalonate but not in response to exogenous sterols. Replacement of span 8 extends both the basal and mevalonate-accelerated half-life about 5-fold. This work begins to define the critical regions for regulated degradation within the membrane domain of HMG-CoA reductase.

Original languageEnglish
Pages (from-to)4236-4246
Number of pages11
JournalJournal of Biological Chemistry
Volume267
Issue number6
StatePublished - Feb 25 1992

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Coenzymes
Hydroxymethylglutaryl CoA Reductases
Oxidoreductases
Membranes
Degradation
Mevalonic Acid
Sterols
Proteins
Sequence Deletion
Mesocricetus
Proteolysis
Galactosidases
Bacteriorhodopsins
Fusion reactions
Cricetulus
LDL Lipoproteins
Half-Life
Ovary
Amino Acids
Mutation

ASJC Scopus subject areas

  • Biochemistry

Cite this

The role of the membrane domain in the regulated degradation of 3-hydroxy-3-methylglutaryl coenzyme a reductase. / Chun, Kristin; Simoni, Robert D.

In: Journal of Biological Chemistry, Vol. 267, No. 6, 25.02.1992, p. 4236-4246.

Research output: Contribution to journalArticle

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