Mechanism of Lysine 48-linked ubiquitin-chain synthesis by the cullin-RING ubiquitin-ligase complex SCF-Cdc34

The process which uses the cyclin-dependent kinase inhibitor Sic1 and its ubiquitination by the cullin-RING ubiquitin ligase SCF and the ubiquitin-conjugating enzyme Cdc34 is discussed. The results showed that Sic1 ubiquitination is separated into two steps which are attachment of the first ubiquitin which is a rate limiting, followed by rapid elongation of a K48-linked ubiquitin chain.