Allosteric ACTion: the varied ACT domains regulating enzymes of amino-acid metabolism

Lang, Eric J. M.; Cross, Penelope J.; Mittelstädt, Gerd; Jameson, Geoffrey B.; Parker, Emily J.

doi:10.1016/j.sbi.2014.10.007

Cited by 73 publications

(117 citation statements)

References 38 publications

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“…The present results establish that the regulatory domains form a side-by-side dimer similar in structure to those formed by other ACT domains (21), including that of TyrH (9). The participation of residues on helix ␣1 and strand ␤2 in the dimer interface of RDPheH is similar to what is seen in other side-by-side ACT domain dimers (10,33).…”

Section: Discussionsupporting

confidence: 79%

“…The regulatory domain of TyrH also contains an ACT domain but it does not bind tyrosine (9), so the presence of an ACT domain in PheH does not in itself establish that the regulatory domain contains a site for phenylalanine. In addition, there is significant diversity in the sites at which ACT domains bind amino acids (21), making it difficult to predict the binding site on an ACT domain without a structure. A recent structure of a bacterial PheH, which is homologous to the catalytic domain of the eukaryotic enzymes, showed phenylalanine bound at a site 15.7 Å from the active site (22), raising the possibility of a separate allosteric site within the catalytic domain.…”

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confidence: 99%

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Identification of the Allosteric Site for Phenylalanine in Rat Phenylalanine Hydroxylase

Zhang

Fitzpatrick

2016

Journal of Biological Chemistry

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Liver phenylalanine hydroxylase (PheH) is an allosteric enzyme that requires activation by phenylalanine for full activity. The location of the allosteric site for phenylalanine has not been established. NMR spectroscopy of the isolated regulatory domain (RDPheH(25-117) is the regulatory domain of PheH lacking residues 1-24) of the rat enzyme in the presence of phenylalanine is consistent with formation of a side-by-side ACT dimer. Six residues in RDPheH(25-117) were identified as being in the phenylalanine-binding site on the basis of intermolecular NOEs between unlabeled phenylalanine and isotopically labeled protein. The location of these residues is consistent with two allosteric sites per dimer, with each site containing residues from both monomers. Site-specific variants of five of the residues (E44Q, A47G, L48V, L62V, and H64N) decreased the affinity of RDPheH(25-117) for phenylalanine based on the ability to stabilize the dimer. Incorporation of the A47G, L48V, and H64N mutations into the intact protein increased the concentration of phenylalanine required for activation. The results identify the location of the allosteric site as the interface of the regulatory domain dimer formed in activated PheH. Phenylalanine hydroxylase (PheH)2 catalyzes a key step in phenylalanine catabolism, the hydroxylation of phenylalanine to tyrosine in the liver using tetrahydropterin (BH 4 ) and oxygen. A deficiency in human PheH increases the level of phenylalanine in the blood, resulting in the inherited disease phenylketonuria (PKU) (1). Thus, the activity of PheH must be tightly controlled to maintain appropriate phenylalanine levels. PheH is activated by phenylalanine and inhibited by BH 4 (2, 3). In addition, phosphorylation of PheH at Ser-16 is reported to decrease the concentration of phenylalanine required to activate PheH (4).Mammalian PheH is a homotetramer, and each monomer contains an N-terminal regulatory domain, a central catalytic domain, and a C-terminal tetramerization domain. The other two aromatic amino acid hydroxylases, tyrosine hydroxylase (TyrH) and tryptophan hydroxylase, have similar architectures.The crystal structures of the catalytic domains of all three enzymes show very similar folds and active sites (5-7), consistent with these enzymes sharing a common catalytic mechanism (8). The structures of the regulatory domains of PheH and TyrH show that both contain ACT domains (5, 9, 10), although the two enzymes are regulated differently (2, 11). To date, there is no published structure of a full-length mammalian PheH, or indeed of any eukaryotic aromatic amino acid hydroxylase, in that the available structures are of proteins lacking the N-terminal regulatory domain, much of the C-terminal tetramerization domain, or both. The structure of a dimeric form of rat PheH containing both the catalytic and regulatory domains but lacking the C-terminal 24 residues required for tetramer formation (5) has provided the present model for the structural basis for activation by phenylalanine. In this structure the...

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Section: Discussionsupporting

confidence: 79%

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confidence: 99%

Identification of the Allosteric Site for Phenylalanine in Rat Phenylalanine Hydroxylase

Zhang

Fitzpatrick

2016

Journal of Biological Chemistry

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“…GspDAH7PS was crystallized in the presence of Mn 2ϩ and chorismate, and its structure was determined at a resolution of 2.75 Å in the space group P6 4 . The asymmetric unit contains two adjacent chains, with each comprising a catalytic (␤/␣) 8 barrel common to all DAH7PS enzymes (residues 106 -362) and a CM domain (residues 1-86) connected by a short linker region (residues 86 -105) (Fig. 6A).…”

Section: Gspdah7psmentioning

confidence: 99%

“…Allosteric regulation is observed both at the pathway entry via DAH7PS and at the branch points from chorismate. All known DAH7PS enzymes share a (␤/␣) 8 barrel catalytic domain, which houses the active site. However, there are distinct variations between DAH7PS enzymes from different organisms in the structural extensions to the barrel that support allostery.…”

mentioning

confidence: 99%

“…Type I␤ enzymes are more varied and either comprise just the core catalytic barrel and show no allosteric regulation or have a discrete domain found at either the N or C termini of the barrel (6). This addition can be either an ACT domain (7,8) (named after the enzymes in which it was originally identified, aspartokinase, chorismate mutase, and TyrA) or a chorismate mutase (CM) enzyme (9), which catalyzes a branch point step of the pathway (Fig. 1).…”

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confidence: 99%

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Interdomain Conformational Changes Provide Allosteric Regulation en Route to Chorismate

Nazmi

Lang

Bai

et al. 2016

Journal of Biological Chemistry

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Multifunctional proteins play a variety of roles in metabolism.Here, we examine the catalytic function of the combined 3-deoxy-D-arabino heptulosonate-7-phosphate synthase (DAH7PS) and chorismate mutase (CM) from Geobacillus sp. DAH7PS operates at the start of the biosynthetic pathway for aromatic metabolites, whereas CM operates in a dedicated branch of the pathway for the biosynthesis of amino acids tyrosine and phenylalanine. In line with sequence predictions, the two catalytic functions are located in distinct domains, and these two activities can be separated and retain functionality. For the full-length protein, prephenate, the product of the CM reaction, acts as an allosteric inhibitor for the DAH7PS. The crystal structure of the full-length protein with prephenate bound and the accompanying small angle x-ray scattering data reveal the molecular mechanism of the allostery. Prephenate binding results in the tighter association between the dimeric CM domains and the tetrameric DAH7PS, occluding the active site and therefore disrupting DAH7PS function. Acquisition of a physical gating mechanism to control catalytic function through gene fusion appears to be a general mechanism for providing allostery for this enzyme.

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Independent catalysis of the short form HisG from Lactococcus lactis

et al. 2016

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Edited by Michael IbbaATP-phosphoribosyltransferase (ATP-PRT) catalyses the first step of histidine biosynthesis. Two different forms of ATP-PRT have been described; the homo-hexameric long form, and the hetero-octameric short form. Lactococcus lactis possesses the short form ATP-PRT comprising four subunits of HisG S , the catalytic subunit, and four subunits of HisZ, a histidyl-tRNA synthetase paralogue. Previous studies have suggested that HisG S requires HisZ for catalysis. Here, we reveal that the dimeric HisG S does display ATP-PRT activity in the absence of HisZ. This result reflects the evolutionary relationship between the long and short form ATP-PRT, which acquired allosteric inhibition and enhanced catalysis via two divergent strategies.

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Allosteric ACTion: the varied ACT domains regulating enzymes of amino-acid metabolism

Cited by 73 publications

References 38 publications

Identification of the Allosteric Site for Phenylalanine in Rat Phenylalanine Hydroxylase

Identification of the Allosteric Site for Phenylalanine in Rat Phenylalanine Hydroxylase

Interdomain Conformational Changes Provide Allosteric Regulation en Route to Chorismate

Independent catalysis of the short form HisG from Lactococcus lactis

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