label: N-terminal glycyl-L-lysyl-L-glutamyl-[protein] + 3 S-adenosyl-L-methionine = N-terminal N,N,N-trimethyl-glycyl-L-lysyl-L-glutamyl-[protein] + 3 S-adenosyl-L-homocysteine + 3 H(+)
label_lc: n-terminal glycyl-l-lysyl-l-glutamyl-[protein] + 3 s-adenosyl-l-methionine = n-terminal n,n,n-trimethyl-glycyl-l-lysyl-l-glutamyl-[protein] + 3 s-adenosyl-l-homocysteine + 3 h(+)