Direct identification of a G protein ubiquitination site by mass spectrometry |
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Authors: | Marotti Louis A Newitt Rick Wang Yuqi Aebersold Ruedi Dohlman Henrik G |
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Institution: | Interdepartmental Neuroscience Program, Yale University School of Medicine, New Haven, Connecticut 06536, USA. |
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Abstract: | Covalent attachment of ubiquitin is well-known to target proteins for degradation. Here, mass spectrometry was used to identify the site of ubiquitination in Gpa1, the G protein alpha subunit in yeast Saccharomyces cerevisiae. The modified residue is located at Lys165 within the alpha-helical domain of Galpha, a region of unknown function. Substitution of Lys165 with Arg (Gpa1(K165R)) results in a substantial decrease in ubiquitination. In addition, yeast expressing the Gpa1(K165R) mutant are moderately resistant to pheromone in growth inhibition assays-a phenotype consistent with enhanced Galpha signaling activity. These findings indicate that the alpha-helical domain may serve to regulate the turnover of Gpa1. |
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