10 Ubikwitynacja

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Ubiquitin	—C—NH—Lys—

Figurę 32-76 Kcactions involvcd in the attachment of ubiquitin to a protein. In the first part of the process. ubiquitin's terminal carboxyl group is joined. via a thioester linkage. to El in a reaction driven by ATP hydrolysis.The activated ubiquitin is subsequenUy transferred to a sulfhydryl group of an E2 and then. in a reaction catalyzed by an E3. to a Lys e-amino group on a condemned protein, thereby flagging the protein for proteolytic degradation by the 26S proteasome.