Two human lysosomal membrane glycoproteins, h-lamp-1 and h-lamp-2, are encoded by genes localized to chromosome 13q34 and chromosome Xq24-25, respectively.

We have isolated previously cDNAs encoding two related human lysosomal membrane glycoproteins, h-lamp-1 and h-lamp-2 (Fukuda, M., Viitala, J., Matteson, J., and Carlsson, S.R. (1988) J. Biol. Chem. 263, 18920-18928). In the present study, we have determined the chromosomal localization of genes for h-lamp-1 and h-lamp-2. By using the method of in situ hybridization, we have localized the gene for h-lamp-1 to chromosome 13q34 and its related gene to chromosome 12p133. The hybridization of h-lamp-1 cDNA to chromosome 12p133 was observed even when probes representing different portions of h-lamp-1 cDNA were used. On ther other hand, the gene for h-lamp-2 were localized to Xq24-25 but no cross-hybridization to chromosome 12p133 was observed even though h-lamp-1 and h-lamp-2 are highly related. These results clearly indicate that human lamp-1 and lamp-2 are coded by separate genes on different chromosomes. The present results support our hypothesis that lamp-1 and lamp-2 diverged early in evolution and they have distinct functions which emerged as soon as eukaryotic cells acquired lysosomes as subcellular compartments.