Structural and functional analyses of mutations of the human phenylalanine hydroxylase gene.
BACKGROUND
Phenylketonuria (PKU) is an inborn error of metabolism that results from a deficiency of phenylalanine hydroxylase (PAH). We demonstrated PAH mutational spectrum from patients with PKU, including 10 novel and 3 tetrahydrobiopterin (BH(4))-responsive mutations. In this study, 11 PAH missense mutations, including 6 novel mutations (P69S, G103S, L293M, G332V, S391I, A447P) found in our previous study, 2 mutations common in east Asian patients with PKU (R243Q, R413P), and 3 tetrahydrobiopterin (BH(4))-responsive mutations (R53H, R241C, R408Q) have been functionally and structurally analyzed.


METHODS
A transient protein overexpression system and an in vitro BH(4)-responsiveness study were used. The effects of PAH missense mutations on the PAH protein structure were also analyzed. To determine the conservation of 12 mutated residues, PAH was aligned using BLAST against full genomic sequences of 221 different species. Model structures of PAH protein and the composite tetramer were constructed using the software program, SHEBA.


RESULTS
No PAH activity was detected for some mutants. However, the residual activities associated with other mutants ranged over a wide spectrum. The missense mutations responsive to BH(4) were not highly conserved throughout the 43 species in the multiple sequence alignment that encode PAH. The composite model structure of PAH revealed that dimer stability was reduced in the BH(4)-responsive mutants, whereas tetramer stability remained normal.


CONCLUSIONS
This expression study analyzed PAH mutations and model structures of mutant PAH proteins are proposed. Correlation between the proposed mutant PAH structures and functions are suggested.
Kim
Sang-Wun
SW
Division of Genetic Disease, Department of Biomedical Sciences, National Institute of Health, Seoul, Republic of Korea.
Jung
Jongsun
J
Oh
Hyun-Jeong
HJ
Kim
Jihong
J
Lee
Kwang-Soo
KS
Lee
Dong-Hwan
DH
Park
Chan
C
Kimm
Kuchan
K
Koo
Soo Kyung
SK
Jung
Sung-Chul
SC
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D019556:COS Cells; D002522:Chlorocebus aethiops; D017931:DNA Primers; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D020125:Mutation, Missense; D010651:Phenylalanine Hydroxylase / Q000737:chemistry / Q000235:genetics*; D011487:Protein Conformation; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D010651:Phenylalanine Hydroxylase