Phenylalanine hydroxylase gene: novel missense mutation in exon 7 causing severe phenylketonuria.

By direct sequence analysis of 94 mutant phenylalanine hydroxylase alleles using polymerase chain reaction-based techniques, we identified a C to T transition in exon 7 of the human phenylalanine hydroxylase gene that is associated with RFLP haplotypes 1 and 4. A leucine for proline substitution at position 281 can be predicted from the nucleotide sequence of the mutant codon. Expression analysis in cultured mammalian cells after site-directed mutagenesis proved that the base substitution is a disease causing gene lesion. Dot-blot hybridization analysis using allele-specific oligonucleotides revealed that 25% of all mutant haplotype 1 alleles in the German population bear this mutation. In addition, this mutation could be detected on one mutant haplotype 4 allele. The fact that this mutation is associated with only 25% of all mutant haplotype 1 alleles suggests that multiple mutations may be associated with this haplotype. The occurrence of several different mutations would be in agreement with the clinical heterogeneity observed in the group of patients whose PKU alleles belong to haplotype 1.

Structure of full-length cDNA coding for sulfatide activator, a Co-beta-glucosidase and two other homologous proteins: two alternate forms of the sulfatide activator.

Full-length cDNA clones have been isolated for an mRNA which codes for four different but homologous proteins--a sulfatide activator protein, a co-beta-clucosidase, and two other proteins of similar structures. The primary structure as deduced from the nucleotide sequence is highly homologous to the precursor of the rat Sertoli cell sulfated glycoprotein 1. The full-length clone was 2,734-bp long, starting from 8 bases above the initiator ATG and terminating with a poly A tail. The nucleotide sequence confirmed an earlier prediction based on the amino acid sequence that a previously published sequence contained errors. On the other hand, the amino acid sequence now closely agrees with the recent revised sequence published by the same group except for several amino acids near the N-terminus. Two alternate forms of the sulfatide activator were detected, differing from each other by the presence or absence of 3-amino acid insertion.