Leucine zipper-bearing kinase (LZK) is a new member of the mixed lineage protein kinase family. We previously cloned a cDNA encoding LZK from a human cerebellum cDNA library. The following studies indicated that LZK serves as a MAPKKK in the JNK/SAPK pathway in cells, and a scaffold protein, JIP-1, enhances LZK-induced JNK/SAPK pathway activation via physical association. Here we report characterization of the gene structure and fine chromosomal mapping of the human LZK gene. Polymerase chain-reaction (PCR) studies indicated that the human LZK coding sequence is composed of 13 exons, and that all the splice acceptor and donor sequences obey the GT-AG rule. Chromosomal localization studies involving FISH mapping demonstrated that the human LZK gene is located at 3q27.