Methylates ribosomal protein L11. L-lysyl-[protein] + 3 S-adenosyl-L-methionine = 3 H(+) + N(6),N(6),N(6)-trimethyl-L-lysyl-[protein] + 3 S-adenosyl-L-homocysteine an N-terminal L-alpha-aminoacyl-[protein] + 3 S-adenosyl-L-methionine = an N-terminal trimethyl-L-alpha-aminoacyl-[protein] + 3 H(+) + 3 S-adenosyl-L-homocysteine Mutant lacks several methyl groups in protein L11 (PubMed:331082, PubMed:372746). Null mutant is perfectly viable (PubMed:7715456, PubMed:331082). Belongs to the methyltransferase superfamily. PrmA family.