Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.1.1 (hexokinase)
 5,274 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using small angle x-ray scattering from solutions of yeast phosphoglycerate kinase, we have measured the radius of gyration of the enzyme both in the presence and in the abscence of ligands. We find that the radius of gyration decreases by 1.09 +/- 0.34 A upon binding both substrates MgATP and 3-phosphoglycerate to form the ternary complex. Smaller decreases, at the limit of the precision of the measurement, were found for the separate binding of MgATP (0.30 +/- 0.50 A). Using computer modeling, it has been estimated that a substrate-induced cleft closure in phosphoglycerate kinase resulting from one lobe rotating 8-14 degrees relative to the other lobe lobe is consistent with this observed change in radius of gyration. We suggest, therefore, that the conformational change that results in the smaller radius of gyration for the ternary complex is a hinge motion of the two lobes which produces a closing of the cleft between the two lobes. The apparent similarity of the ligand-induced change in phosphoglycerate kinase to the cleft closure in hexokinase suggests that this kind of conformational change may prove to be a rather general kinase phenomenon (Bennett, W.S., and Steitz T.A. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 4848-4852; Anderson, C.M., Zucker, F.H., and Steitz, T.A. (1979) Science 204, 375-380).
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PMID:Substrate binding closes the cleft between the domains of yeast phosphoglycerate kinase. 38 70

The functionally diverse actin, hexokinase, and hsp70 protein families have in common an ATPase domain of known three-dimensional structure. Optimal superposition of the three structures and alignment of many sequences in each of the three families has revealed a set of common conserved residues, distributed in five sequence motifs, which are involved in ATP binding and in a putative interdomain hinge. From the multiple sequence alignment in these motifs a pattern of amino acid properties required at each position is defined. The discriminatory power of the pattern is in part due to the use of several known three-dimensional structures and many sequences and in part to the "property" method of generalizing from observed amino acid frequencies to amino acid fitness at each sequence position. A sequence data base search with the pattern significantly matches sugar kinases, such as fuco-, glucono-, xylulo-, ribulo-, and glycerokinase, as well as the prokaryotic cell cycle proteins MreB, FtsA, and StbA. These are predicted to have subdomains with the same tertiary structure as the ATPase subdomains Ia and IIa of hexokinase, actin, and Hsc70, a very similar ATP binding pocket, and the capacity for interdomain hinge motion accompanying functional state changes. A common evolutionary origin for all of the proteins in this class is proposed.
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PMID:An ATPase domain common to prokaryotic cell cycle proteins, sugar kinases, actin, and hsp70 heat shock proteins. 132 28

Horse muscle phosphoglycerate kinase (PGK) is a monomer folded into two widely distant domains. In the glycolytic pathway, this enzyme catalyzes the first reaction that produces ATP. It was suggested, by analogy with yeast hexokinase, that a hinge-bending motion may be induced by the binding of specific substrates to the protein. To analyze such a motion, or any structural changes induced by ligand binding, fluorescence anisotropy decay of tryptophan residues in free and liganded PGK was studied. At 293 K, for the free protein and the binary complex with 3-phosphoglycerate, a single correlation time of 26 ns was observed, corresponding to the rotation of the overall protein, whereas upon addition of MgADP, this correlation time decreased to 10 ns. Such a decrease cannot be merely due to a change of the protein's shape and volume. To explain this, it was suggested that the fluorescence anisotropy decay of the PGK-MgADP complex corresponded to the rotation of the only buried tryptophan (Trp 335). The rotational paths of this tryptophan, in the presence and absence of the nucleotide, were established by potential energy minimization calculations. The results indicated that MgADP induces a displacement of helix alpha-13 that decreases the rotational energy barrier of Trp 335 from 16 kcal/mol in the free protein to 8 kcal/mol in the complex.
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PMID:The effects of ligands on the conformation of phosphoglycerate kinase: fluorescence anisotropy decay and theoretical interpretation. 208 55

The natures and roles of ligand-induced conformational changes are described in terms of the influence of the ligand on the equilibrium distribution of the protein structure among various conformational states. A very commonly observed conformational change is produced by a ligand binding into a cleft that lies between two domains and then closing the cleft through a hinge-like motion. Such a change in hexokinase serves to bring potential catalytic groups into the active site and to provide a binding site for the three phosphates of ATP. Flexibility in gene regulatory proteins such as the Escherichia coli catabolite activator protein and lac repressor may be important in the dual requirement for rapid diffusion of the proteins along the DNA as well as specific recognition of base sequences. A second role for flexibility in this class of proteins is to reduce their affinity for affinity for DNA, without reducing their capacity to discriminate among sequences.
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PMID:Ligand-induced conformational changes in proteins. 630 81

X-ray structure analysis of actin and of the NH2-terminal domain of the heat-shock cognate protein Hsc70 has revealed an unexpected extensive structural similarity between these two molecules. Despite the absence of significant similarity of their amino acid sequences, both proteins share the same core architecture and a common nucleotide binding site resembling the structure of hexokinase. All three are ATPases or kinases and bind ATP in association with Mg2+ or Ca2+. The common fold consists of two alpha/beta domains, which are connected by a putative hinge with an ATP-binding site situated between the domains. Each domain contains a five-stranded beta-sheet of identical topology, which suggests that the molecules may have evolved by gene duplication. From a comparison of the three aligned structures, a fingerprint sequence of the adenine nucleotide binding pocket was derived, which predicted that members of the glycerol kinase family should also have a similar fold of their nucleotide binding domain. This was later confirmed when the X-ray structure was published. Data base search with a refined consensus sequence has retrieved other sugar kinases, as well as the prokaryotic cell cycle proteins FtsA, MreB, and StbA, and two Escherichia coli phosphatases. These proteins are predicted to possess a structure similar to actin in the common core region. As exemplified for actin, Hsc70, and glycerol kinase, the diversity of biological function is provided by the polymorphism of the loops joining the beta-strands and helices in the core region and by inserted domains that show high variability.
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PMID:The actin fold. 778 19

Knowledge of the structure of actin in its various conformational states is important for understanding the diverse motile activities carried out by eukaryotic cells. Profilin:actin crystals provide a unique system for studying conformational states of actin, because they exhibit a high degree of polymorphism in response to environmental conditions while maintaining crystalline order. A preliminary comparison of two states of profilin:beta-actin crystals shows that crystal polymorphism involves movements of actin subdomains at hinge points homologous to those found in hexokinase, a protein whose polypeptide fold is related to actin. The homology of the hinge points in actin to those in hexokinase suggests that actin subdomain movements in profilin:beta-actin crystals have functional significance. We discuss how these movements could be related to structural transitions between states of filamentous actin in muscle contraction.
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PMID:Structural studies on the ribbon-to-helix transition in profilin: actin crystals. 778 53

A normal mode analysis of the closed form of dimeric citrate synthase has been performed. The largest-amplitude collective motion predicted by this method compares well with the crystallographically observed hinge-bending motion. Such a result supports those obtained previously in the case of hinge-bending motions of smaller systems, such as lysozyme or hexokinase. Taken together, all these results suggest that low-frequency normal modes may become useful for determining a first approximation of the conformational path between the closed and open forms of these proteins.
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PMID:Hinge-bending motion in citrate synthase arising from normal mode calculations. 874 51

The activity of many proteins induces conformational transitions by hinge-bending, which involves the movement of relatively rigid parts of a protein about flexible joints. We present an algorithm to identify and visualize the movements of rigid domains about common hinges in proteins. In comparing two structures, the method partitions a protein into domains of preserved geometry. The domains are extracted by an adaptive selection procedure using least-squares fitting. The user can maintain the spatial connectivity of the domains and filter significant structural differences (domain movements) from noise in the compared sets of atomic coordinates. The algorithm subsequently characterizes the relative movements of the found domains by effective rotation axes (hinges). The method is applied to several known instances of domain movements in protein structures, namely, in lactoferrin, hexokinase, actin, the extracellular domains of human tissue factor, and the receptor of human growth factor. The results are visualized with the molecular graphics package VMD (Humphrey et al., J. Mol. Graphics 14(1):33-38, 1996). Applications of the algorithm to the analysis of conformational changes in proteins and to biomolecular docking are discussed.
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PMID:Protein domain movements: detection of rigid domains and visualization of hinges in comparisons of atomic coordinates. 929 63

Previous crystallographic investigations have shown that actin can undergo large conformational changes, even when complexed to the same actin binding protein. We have conducted a formal analysis of domain motions in actin, using the four available crystal structures, to classify the mechanism as either hinge or shear and to quantify the magnitude of these changes. We demonstrate that actin consists of two rigid cores, a semi-rigid domain and three conformationally variable extended loops. Confirming predictions about the nature of the domain rotation in actin based on its structural similarity to hexokinase, we show, using an algorithm previously used only to identify protein hinges, that residues at the interface between the two rigid cores undergo a shear between alternative conformations of actin. Rotations of less than 7 degrees in the torsion angles of five residues in the polypeptides that connect the rigid cores enable one actin conformation to be transformed into another. Because these torsion angle changes are small, the interface between the domains is maintained. In addition, we show that actin secondary structure elements, including those outside the rigid cores, are conformationally invariant among the four crystal structures, even when actin is complexed to different actin binding proteins. Finally, we demonstrate that the current F-actin models are inconsistent with the principles of actin conformational change identified here.
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PMID:Domain motions in actin. 966 49

Actin is one of the most highly conserved eukaryotic proteins. There are no amino acid changes between the chicken and human skeletal muscle isoforms, and the most dissimilar actins still share more than 85% sequence identity [1]. We suggest that large discrete internal modes of freedom within the actin filament may account for a significant component of this conservation, since each subunit must make multiple specific interactions with neighboring subunits. In support of this, we find that the same state of tilt of the actin subunit exists in both yeast and vertebrate striated muscle actin, and that in both the two domains undergo a "propeller rotation." A similar movement of domains has also been seen in hexokinase, Hsc70, and Arp2/3, all structural homologs of actin, suggesting that such an interdomain hinge motion is common to proteins in this superfamily. Subunit-subunit interactions within the actin filament involve sequence insertions that are not present in MreB, a bacterial homolog of actin. Remarkably, we find that in the tilted state actin subunits make new contacts with neighboring subunits that also involve these inserts, suggesting a key role for these elements in F-actin polymorphism.
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PMID:A new internal mode in F-actin helps explain the remarkable evolutionary conservation of actin's sequence and structure. 1193 26


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