A DNA encoding a variant of a protein having a loop region and six hydrophobic helixes which is involved in excretion of L-lysine to outside of a cell is described, wherein the DNA encodes a mutant protein which does not contain the loop region that is present in the wild-type protein. The mutant protein facilitates excretion of L-lysine, L-arginine, or both to the outside of the cell of a methanol assimilating bacterium when the DNA is introduced into the bacterium. Specifically, lysE24 is introduced into a methanol assimilating bacterium such as Methylophilus bacteria which results in improved L-amino acid productivity, especially production of L-lysine and L-arginine.