N-acetyltransferase that mediates the acetylation of the N-terminal residues of alpha- and beta-tubulin. acetyl-CoA + N-terminal L-methionyl-[tubulin] = CoA + H(+) + N-terminal N(alpha)-acetyl-L-methionyl-[tubulin] Belongs to the acetyltransferase family. GNAT subfamily.