Title

G Protein Mono-ubiquitination by the Rsp5 Ubiquitin Ligase

UMMS Affiliation

Program in Systems Biology

Date

3-27-2009

Document Type

Article

Medical Subject Headings

Endosomal Sorting Complexes Required for Transport; GTP-Binding Protein alpha Subunits, Gq-G11; Mutation; Proteasome Endopeptidase Complex; Protein Processing, Post-Translational; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Ubiquitin-Protein Ligase Complexes; Ubiquitination; Vacuoles

Disciplines

Biochemistry

Abstract

Emerging evidence suggests that ubiquitination serves as a protein trafficking signal in addition to its well characterized role in promoting protein degradation. The yeast G protein alpha subunit Gpa1 represents a rare example of a protein that undergoes both mono- and poly-ubiquitination. Whereas mono-ubiquitinated Gpa1 is targeted to the vacuole, poly-ubiquitinated Gpa1 is directed instead to the proteasome. Here we investigate the structural requirements for mono- and poly-ubiquitination of Gpa1. We find that variants of Gpa1 engineered to be unstable are more likely to be poly-ubiquitinated and less likely to be mono-ubiquitinated. In addition, mutants that cannot be myristoylated are no longer mono-ubiquitinated but are still polyubiquitinated. Finally, we show that the ubiquitin ligase Rsp5 is necessary for Gpa1 mono-ubiquitination in vivo and that the purified enzyme is sufficient to catalyze Gpa1 mono-ubiquitination in vitro. Taken together, these data indicate that mono- and poly-ubiquitination have distinct enzyme and substrate recognition requirements; whereas poly-ubiquitination targets misfolded protein for degradation, a distinct ubiquitination apparatus targets the fully mature, fully myristoylated G protein for mono-ubiquitination and delivery to the vacuole.

Rights and Permissions

Citation: Torres MP, Lee MJ, Ding F, Purbeck C, Kuhlman B, Dokholyan NV, Dohlman HG. G Protein Mono-ubiquitination by the Rsp5 Ubiquitin Ligase. J Biol Chem. 2009 Mar 27;284(13):8940-50. doi: 10.1074/jbc.M809058200. Link to article on publisher's site

Comments

At the time of publication, Michael J. Lee was not yet affiliated with the University of Massachusetts Medical School.

Related Resources

Link to Article in PubMed

Journal Title

The Journal of biological chemistry

PubMed ID

19176477