L-lysyl-[ribulose-1,5-bisphosphate carboxylase] + 3 S-adenosyl-L-methionine = N(6),N(6),N(6)-trimethyl-L-lysyl-[ribulose-1,5-bisphosphate carboxylase] + 3 S-adenosyl-L-homocysteine + 3 H(+) — reaction