Linked Life Data

9799096

Source:http://linkedlifedata.com/resource/pubmed/id/9799096

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1998-11-10
pubmed:databankReference
pubmed:abstractText
The molecular basis for the metabolic defect in patients with phenylketonuria has been characterized for seven missense point mutations (R252G/Q, L255V/S, A259V/T and R270S) and a termination mutation (G272X) in an evolutionarily conserved motif of exon 7 in the catalytic domain of the human phenylalanine hydroxylase (hPAH) gene. The mutations were expressed in three heterologous in vitro systems. When expressed as fusion proteins with maltose-binding protein in Escherichia coli five of the mutant proteins demonstrated a defect in the normal ability of hPAH to fold and assemble as homotetramer/dimer, and they were mostly recovered as inactive aggregated forms. Only for the R252Q and L255V mutants were catalytically active tetramer and dimer recovered and for R252G some dimer, i.e. 20% (R252Q, tetramer), 44% (L255V, tetramer) and 4.4% (R252G, dimer) of the activity for the respective wild-type (wt) forms. When expressed by a coupled in vitro transcription-translation system, all the mutant enzymes were recovered as a mixture of non-phosphorylated and phosphorylated forms with a low homospecific activity (i.e. maximum 11% of wt-hPAH for the L255V mutant). When transiently expressed in human embryonic kidney (A293) cells a very low level of immunoreactive PAH protein was recovered in spite of normal PAH mRNA levels. All these mutations resulted in variant hPAH proteins which revealed a defect in oligomerization, an increased sensitivity to limited proteolysis in vitro, reduced cellular stability and a variable reduction in their catalytic activity. All these effects seem to result from structural perturbations of the monomer, and based on the crystal structure of the catalytic domain of hPAH, an explanation is provided for the impact of the mutations on the folding and oligomerization of the monomers.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0014-2956
pubmed:author
pubmed:issnType
Print
pubmed:day
1
pubmed:volume
257
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1-10
pubmed:dateRevised
2007-7-23
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Partial characterization and three-dimensional-structural localization of eight mutations in exon 7 of the human phenylalanine hydroxylase gene associated with phenylketonuria.
pubmed:affiliation
Department of Biochemistry and Molecular Biology, University of Bergen, Norway.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't