6HYC image
Deposition Date 2018-10-19
Release Date 2019-06-05
Last Version Date 2024-01-24
Entry Detail
PDB ID:
6HYC
Keywords:
Title:
The structure of full-length human phenylalanine hydroxylase in complex with the cofactor and negative regulator tetrahydrobiopterin
Biological Source:
Source Organism:
Homo sapiens (Taxon ID: 9606)
Method Details:
Experimental Method:
Resolution:
3.18 Å
R-Value Free:
0.31
R-Value Work:
0.26
R-Value Observed:
0.26
Space Group:
C 1 2 1
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Phenylalanine-4-hydroxylase
Gene (Uniprot):PAH
Chain IDs:A (auth: D), B (auth: A), C, D (auth: B)
Chain Length:452
Number of Molecules:4
Biological Source:Homo sapiens
Ligand Molecules
Primary Citation
Structure of full-length human phenylalanine hydroxylase in complex with tetrahydrobiopterin.
Proc.Natl.Acad.Sci.USA 116 11229 11234 (2019)
PMID: 31118288 DOI: 10.1073/pnas.1902639116

Abstact

Phenylalanine hydroxylase (PAH) is a key enzyme in the catabolism of phenylalanine, and mutations in this enzyme cause phenylketonuria (PKU), a genetic disorder that leads to brain damage and mental retardation if untreated. Some patients benefit from supplementation with a synthetic formulation of the cofactor tetrahydrobiopterin (BH4) that partly acts as a pharmacological chaperone. Here we present structures of full-length human PAH (hPAH) both unbound and complexed with BH4 in the precatalytic state. Crystal structures, solved at 3.18-Å resolution, show the interactions between the cofactor and PAH, explaining the negative regulation exerted by BH4 BH4 forms several H-bonds with the N-terminal autoregulatory tail but is far from the catalytic FeII Upon BH4 binding a polar and salt-bridge interaction network links the three PAH domains, explaining the stability conferred by BH4 Importantly, BH4 binding modulates the interaction between subunits, providing information about PAH allostery. Moreover, we also show that the cryo-EM structure of hPAH in absence of BH4 reveals a highly dynamic conformation for the tetramers. Structural analyses of the hPAH:BH4 subunits revealed that the substrate-induced movement of Tyr138 into the active site could be coupled to the displacement of BH4 from the precatalytic toward the active conformation, a molecular mechanism that was supported by site-directed mutagenesis and targeted molecular dynamics simulations. Finally, comparison of the rat and human PAH structures show that hPAH is more dynamic, which is related to amino acid substitutions that enhance the flexibility of hPAH and may increase the susceptibility to PKU-associated mutations.

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