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  • Structural characterization of the N-terminal autoregulatory sequence of phenylalanine hydroxylase
    Horne, James ...
    Phenylalanine hydroxylase (PAH) is activated by its substrate phenylalanine, and through phosphorylation by cAMP-dependent protein kinase at Ser16 in the N-terminal autoregulatory sequence of the ... enzyme. The crystal structures of phosphorylated and unphosphorylated forms of the enzyme showed that, in the absence of phenylalanine, in both cases the N-terminal 18 residues including the phosphorylation site contained no interpretable electron density. We used nuclear magnetic resonance (NMR) spectroscopy to characterize this N-terminal region of the molecule in different stages of the regulatory pathway. A number of sharp resonances are observed in PAH with an intact N-terminal region, but no sharp resonances are present in a truncation mutant lacking the N-terminal 29 residues. The N-terminal sequence therefore represents a mobile flexible region of the molecule. The resonances become weaker after the addition of phenylalanine, indicating a loss of mobility. The peptides corresponding to residues 2-20 of PAH have different structural characteristics in the phosphorylated and unphosphorylated forms, with the former showing increased secondary structure. Our results support the model whereby upon phenylalanine binding, the mobile N-terminal 18 residues of PAH associate with the folded core of the moleculeč phosphorylation may facilitate this interaction.
    Source: Protein science. - ISSN 0961-8368 (Letn. 11, št. 8, 2002, str. 2041-2047)
    Type of material - article, component part ; adult, serious
    Publish date - 2002
    Language - english
    COBISS.SI-ID - 2648346

source: Protein science. - ISSN 0961-8368 (Letn. 11, št. 8, 2002, str. 2041-2047)
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