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Published March 24, 1989 | public
Journal Article

A multiubiquitin chain is confined to specific lysine in a targeted short-lived protein


The ubiquitin-dependent degradation of a test protein β-galactosidase (βgal) is preceded by ubiquitination of beta gal. The many (from 1 to more than 20) ubiquitin moieties attached to a molecule of beta gal occur as an ordered chain of branched ubiquitin-ubiquitin conjugates in which the carboxyl-terminal Gly⁷⁶ of one ubiquitin is jointed to the internal Lys⁴⁸ of an adjacent ubiquitin. This multiubiquitin chain is linked to one of two specific Lys residues in βgal. These same Lys residues have been identified by molecular genetic analysis as components of the aminoterminal degradation signal in βgal. The experiments with ubiquitin mutated at its Lys⁴⁸ residue indicate that the multiubiquitin chain in a targeted protein is essential for the degradation of the protein.

Additional Information

© 1989 American Association for the Advancement of Science. 3 October 1988; accepted 20 January 1989. We thank M. Chow, D. Finley, S. Jentsch, M. Hochstrasser, and J. McGrath for helpful discussions; B. Bartel, D. Finley, and M. Hochstrasser for comments on the manuscript; and B. Doran for secretarial assistance. Supported by NIH grants GM35803 and AG07470 (V.C.), NIH grants GM31530 and DK39520 (A.V.), a fellowship from the European Molecular Biology Organization (A.B.), and a fellowship from the Jane Coffin Childs Memorial Fund for Medical Research (D.K.G.).

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