Effects of double amino-acid substitution polymorphism in acid beta-galactosidase gene in two inbred strains of mice.
We observed earlier that there are 5 nucleotide polymorphisms in the protein coding sequence of the acid beta-galactosidase gene between the C57BL/6J and DBA/2J strains of mice. Two of them result in amino acid substitutions. Consequences of the difference in the primary amino acid sequence were studied by introducing the two DBA polymorphisms into the C57BL cDNA, individually and in combination, by oligonucleotide-directed mutagenesis and expressing the resultant cDNAs in the COS-1 cell expression system. Introduction of one polymorphism, Asn517-->Asp into the C57BL cDNA, did not alter the acid beta-galactosidase activity in the transfected COS-1 cells, while introduction of Gly539-->Arg completely abolished the catalytic activity. When both polymorphisms were introduced together, as in the DBA mice, however, the acid beta-galactosidase activity was restored to that of the C57BL level. Thus, Asn517-->Asp appears to counteract the activity-abolishing effect of Gly539-->Arg, although it does not by itself raise the catalytic activity. All four types of cDNA generated similarly large amounts of stable mRNA in COS-1 cells. These results do not explain the significantly low acid beta-galactosidase activity in tissues of DBA mice, described earlier and also confirmed in this study.
Hara
Y
Y
Department of Neurology, University of North Carolina School of Medicine, Chapel Hill 27599.
Nishimoto
J
J
Suzuki
K
K
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011110:Polymorphism, Genetic; D014162:Transfection; D001616:beta-Galactosidase / Q000235:genetics* / Q000378:metabolism
C021502:acid beta-galactosidase; D001616:beta-Galactosidase