A 25 , Kilodalton Ubiquitin Carrier Protein ( E 2 ) Catalyzes Multi-ubiquitin Chain Synthesis via Lysine 48 of Ubiquitin *

Target protein multi-ubiquitination involving lysine 48 of ubiquitin (Ub) is known to occur during protein degradation in the ATPand Ub-dependent proteolytic pathway (Chau, V., Tobias, J. W., Bachmair, A., Marriott, D., Ecker, D. J., Gonda, D. K., and Varshavsky, A. (1989) Science 243, 1576-1583). However, little is known about the enzymatic mechanism of… (More)