Characterization of a temperature-sensitive mutant of a ubiquitin- conjugating enzyme and its use as a heat-inducible degradation signal

Prasad Tongaonkar, Konrad Beck, Ujwal P. Shinde, Kiran Madura

Research output: Contribution to journalArticle

9 Scopus citations

Abstract

The ubiquitin/proteasome pathway is a highly conserved mechanism of proteolysis in all eukaryotes. Ubiquitin (Ub) is conjugated to proteolytic substrates through the sequential action of ubiquitin-activating (E1/Uba) and ubiquitin-conjugating (E2/Ubc) enzymes. The mechanism of substrate recognition and ubiquitination is an area of active investigation, and we have begun a site-directed mutagenesis approach to define the biochemical and biophysical properties of ubiquitin-conjugating enzymes. We have characterized a specific mutation in Ubc4 (Ubc4(P62S)) which was previously shown to cause a temperature-sensitive growth defect in several other Ubc's. Ubc4(P62S) was rapidly degraded in vivo, contributing to the loss of function. However, reconstitution experiments revealed that the catalytic activity of Ubc4(P62S) was reversibly inactivated at 37°C, demonstrating that the primary defect of Ubc4(P62S) is its inability to form a ubiquitin thioester bond at high temperature. The in vivo defect is compounded by increased susceptibility of Ubc4(P62S) to degradation by the ubiquitin/proteasome pathway. We have exploited the temperature-dependent degradation of the P62S mutant to destabilize an otherwise stable test protein (glutathione S-transferase). The use of this mutant may provide a useful cis-acting temperature-inducible degradation signal.

Original languageEnglish (US)
Pages (from-to)263-269
Number of pages7
JournalAnalytical Biochemistry
Volume272
Issue number2
DOIs
StatePublished - Aug 1 1999

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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