| Human light chain 3 / MAP1LC3B , an autophagosomal ortholog of yeast Atg 8 , is conjugated to phospholipid ( PL ) via ubiquitylation like reactions mediated by human Atg 7 and Atg 3 . ^^^ An in vitro assay showed that Gly ( 120 ) is essential for carboxyl terminal cleavage by human Atg4B as well as for formation of the intermediates Atg 7 MAP1LC3B ( ubiquitin activating enzyme substrate ) and Atg 3 MAP1LC3B ( ubiquitin carrier protein substrate ) . ^^^ |