Four new adenosine deaminase mutations, altering a zinc-binding histidine, two conserved alanines, and a 5' splice site.

Published

Journal Article

Three new missense mutations (H15D, A83D, and A179D) and a new splicing defect (573 + IG-->A) in the 5' splice site of intron 5 were among six mutant adenosine deaminase (ADA) alleles found in three unrelated patients with severe combined immunodeficiency disease, the most common phenotype associated with ADA deficiency. When expressed in vitro, the H15D, A83D, and A179D proteins lacked detectable ADA activity. The splicing defect caused skipping of exon 5, resulting in premature termination of translation and a reduced level of mRNA. H15D is the first naturally occurring mutation of a residue that coordinates directly with the enzyme-associated zinc ion. Molecular modeling based on the atomic coordinates of murine ADA suggests that the D15 mutation would create a cavity or gap between the zinc ion and the side chain carboxylate of D15. This could alter the ability of zinc to activate a water molecule postulated to play a role in the catalytic mechanism. A83 and A179 are not directly involved in the active site, but are conserved residues located respectively in alpha helix 4 and beta strand 4 of the alpha/beta barrel. Replacement of these small hydrophobic Ala residues with the charged, more bulky Asp side chain may distort ADA structure and affect enzyme stability or folding.

Full Text

Duke Authors

Cited Authors

  • Santisteban, I; Arredondo-Vega, FX; Kelly, S; Debre, M; Fischer, A; Pérignon, JL; Hilman, B; elDahr, J; Dreyfus, DH; Gelfand, EW

Published Date

  • 1995

Published In

Volume / Issue

  • 5 / 3

Start / End Page

  • 243 - 250

PubMed ID

  • 7599635

Pubmed Central ID

  • 7599635

International Standard Serial Number (ISSN)

  • 1059-7794

Digital Object Identifier (DOI)

  • 10.1002/humu.1380050309

Language

  • eng

Conference Location

  • United States