Targeted replacement of hGGT2 residues with wild-type hGGT1 amino acids does not restore autocatalytic maturation. Whole cell lysates from HEK293T cells transfected with either empty vector (lane1), wild-type hGGT1 cDNA (lane 2), GGT2-1 cDNA (lane 3), or mutant GGT2-1 alleles (lanes 4–7) were resolved by SDS-PAGE and electroblotted onto nitrocellulose. Immunoblotting was carried out using the GGT129 antibody. For labeling the hGGT2-1 lanes: hGGT2-1, wild-type hGGT2-1; hGGT2-1(C/E), hGGT2-1(W192C;Y193E); hGGT2-1(C/E/D/D), hGGT2-1(W192C;Y193E;T422D;T423D); hGGT2-1(C/E/S), hGGT2-1(W192C;Y193E;L451S); and hGGT2-1 (C/E/D/D/S), hGGT2-1(W192C;Y193E;T422D;T423D;L451S).