Open AccessHuman beta-hexosaminidase alpha chain: coding sequence and homology with the beta chain.
Author(s) -
Rachel Myerowitz,
R Ichard L. Piekarz,
Elizabeth F. Neufeld,
Thomas B. Shows,
Kazuyuki Suzuki
Publication year - 1985
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.82.23.7830
Subject(s) - complementary dna , biology , microbiology and biotechnology , untranslated region , peptide sequence , nucleic acid sequence , cdna library , coding region , alpha chain , base pair , homology (biology) , protein primary structure , genetics , amino acid , gene , messenger rna
We have isolated a cDNA clone, p beta H alpha-5, from an adult human liver library that contains the entire coding sequence of the alpha chain of beta-hexosaminidase. The cDNA insert of p beta H alpha-5 is 1944 base pairs long and contains a 168-base-pair 5' untranslated region, a 186-base-pair 3' untranslated region, and an open reading frame of 1587 base pairs corresponding to 529 amino acids (Mr, 60,697). The first 17-22 amino acids satisfy the requirements of a signal sequence. A striking sequence homology with a published partial amino acid sequence for the beta chain [O'Dowd, B. F., Quan, F., Willard, H. F., Lamhonwah, A. M., Korneluk, R. G., Lowden, J. A., Gravel, R. A. & Mahuran, D. J. (1985) Proc. Natl. Acad. Sci. USA 82, 1184-1188] suggests that both chains may have evolved from a common ancestor. A shorter alpha-chain cDNA was found to hybridize to the long arm of chromosome 15, the known location for the alpha-chain gene. In addition, we isolated another alpha-chain cDNA clone, p beta H alpha-4, from a simian virus 40-transformed human fibroblast library that contained an extra 453-base-pair piece at its 3' end. A probe consisting of this additional sequence hybridized exclusively to a single mRNA species (2.6 kilobases) in mRNA preparations from cultured human fibroblasts. In contrast, p beta H alpha-5 hybridized to both a 2.1-kilobase major and a 2.6-kilobase minor mRNA species in these same mRNA preparations, indicating the presence of two distinct alpha-chain mRNA species differing at the 3' end. Fibroblasts from an Ashkenazi Jewish patient with classic Tay-Sachs disease were deficient in both species of mRNA, confirming their genetic relationship.