Reaction catalyzed by RING-type E3 ubiquitin transferase (2.3.2.27)

	[PUB54-RING domain-ubiquitin-carrier protein Ubc4/5]-S-ubiquitinyl-L-cysteine	+		[acceptor protein]-L-lysine	=		[PUB54-RING domain-ubiquitin-carrier protein Ubc4/5]-L-cysteine	+		[acceptor protein]-N6-ubiquitinyl-L-lysine
	[PUB54-RING domain-ubiquitin-carrier protein Ubc4/5]-S-ubiquitinyl-L-cysteine	+		[acceptor protein]-L-lysine	=		[PUB54-RING domain-ubiquitin-carrier protein Ubc4/5]-L-cysteine	+		[acceptor protein]-N6-ubiquitinyl-L-lysine