GO:0034450

Catalysis of the reaction: ATP + ubiquitin + protein N-ubiquityl(n)lysine = AMP + diphosphate + protein N-ubiquityl(n+1)lysine. This reaction is the ligation of ubiquitin groups, via isopeptide bonds, to extend the length of the multiubiquitin chain attached to a substrate protein. [GOC:mah, GOC:mcc, PMID:10089879, PMID:17190603]