1
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Gizak A, Duda P, Wisniewski J, Rakus D. Fructose-1,6-bisphosphatase: From a glucose metabolism enzyme to multifaceted regulator of a cell fate. Adv Biol Regul 2019; 72:41-50. [PMID: 30871972 DOI: 10.1016/j.jbior.2019.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Revised: 03/04/2019] [Accepted: 03/05/2019] [Indexed: 06/09/2023]
Abstract
Fructose-1,6-bisphosphatase (FBPase) is one of the ancient, evolutionarily conserved enzymes of carbohydrate metabolism. It has been described for a first time in 1943, however, for the next half a century mostly kinetic and structural parameters of animal FBPases have been studied. Discovery of ubiquitous expression of the muscle isozyme of FBPase, thus far considered to merely regulate glycogen synthesis from carbohydrate precursors, and its nuclear localisation in several cell types has risen new interest in the protein, resulting in numerous publications revealing complex functions/properties of FBPase. This review summarises the current knowledge of FBPase in animal cells providing evidence that the enzyme merits the name of moonlighting protein.
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Affiliation(s)
- Agnieszka Gizak
- Department of Molecular Physiology and Neurobiology, Wroclaw University, Wroclaw, Poland
| | - Przemyslaw Duda
- Department of Molecular Physiology and Neurobiology, Wroclaw University, Wroclaw, Poland
| | - Janusz Wisniewski
- Department of Molecular Physiology and Neurobiology, Wroclaw University, Wroclaw, Poland
| | - Dariusz Rakus
- Department of Molecular Physiology and Neurobiology, Wroclaw University, Wroclaw, Poland.
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2
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Gao Y, Shen L, Honzatko RB. Central cavity of fructose-1,6-bisphosphatase and the evolution of AMP/fructose 2,6-bisphosphate synergism in eukaryotic organisms. J Biol Chem 2014; 289:8450-61. [PMID: 24436333 DOI: 10.1074/jbc.m114.548586] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The effects of AMP and fructose 2,6-bisphosphate (Fru-2,6-P2) on porcine fructose-1,6-bisphosphatase (pFBPase) and Escherichia coli FBPase (eFBPase) differ in three respects. AMP/Fru-2,6-P2 synergism in pFBPase is absent in eFBPase. Fru-2,6-P2 induces a 13° subunit pair rotation in pFBPase but no rotation in eFBPase. Hydrophilic side chains in eFBPase occupy what otherwise would be a central aqueous cavity observed in pFBPase. Explored here is the linkage of AMP/Fru-2,6-P2 synergism to the central cavity and the evolution of synergism in FBPases. The single mutation Ser(45) → His substantially fills the central cavity of pFBPase, and the triple mutation Ser(45) → His, Thr(46) → Arg, and Leu(186) → Tyr replaces porcine with E. coli type side chains. Both single and triple mutations significantly reduce synergism while retaining other wild-type kinetic properties. Similar to the effect of Fru-2,6-P2 on eFBPase, the triple mutant of pFBPase with bound Fru-2,6-P2 exhibits only a 2° subunit pair rotation as opposed to the 13° rotation exhibited by the Fru-2,6-P2 complex of wild-type pFBPase. The side chain at position 45 is small in all available eukaryotic FBPases but large and hydrophilic in bacterial FBPases, similar to eFBPase. Sequence information indicates the likelihood of synergism in the FBPase from Leptospira interrogans (lFBPase), and indeed recombinant lFBPase exhibits AMP/Fru-2,6-P2 synergism. Unexpectedly, however, AMP also enhances Fru-6-P binding to lFBPase. Taken together, these observations suggest the evolution of AMP/Fru-2,6-P2 synergism in eukaryotic FBPases from an ancestral FBPase having a central aqueous cavity and exhibiting synergistic feedback inhibition by AMP and Fru-6-P.
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Affiliation(s)
- Yang Gao
- From the Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa 50011
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3
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Shi R, Chen ZY, Zhu DW, Li C, Shan Y, Xu G, Lin SX. Crystal structures of human muscle fructose-1,6-bisphosphatase: novel quaternary states, enhanced AMP affinity, and allosteric signal transmission pathway. PLoS One 2013; 8:e71242. [PMID: 24086250 PMCID: PMC3785478 DOI: 10.1371/journal.pone.0071242] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 06/27/2013] [Indexed: 11/18/2022] Open
Abstract
Fructose-1,6-bisphosphatase, a key enzyme in gluconeogenesis, is subject to metabolic regulation. The human muscle isozyme is significantly more sensitive towards the allosteric inhibitor, AMP, than the liver isoform. Here we report crystal structures and kinetic studies for wild-type human muscle Fru-1,6-Pase, the AMP-bound (1.6 Å), and product-bound complexes of the Q32R mutant, which was firstly introduced by an error in the cloning. Our high-resolution structure reveals for the first time that the higher sensitivity of the muscle isozyme towards AMP originates from an additional water-mediated, H-bonded network established between AMP and the binding pocket. Also present in our structures are a metaphosphate molecule, alternate conformations of Glu97 coordinating Mg2+, and possible metal migration during catalysis. Although the individual subunit is similar to previously reported Fru-1,6-Pase structures, the tetrameric assembly of all these structures deviates from the canonical R- or T-states, representing novel tetrameric assemblies. Intriguingly, the concentration of AMP required for 50% inhibition of the Q32R mutant is increased 19-fold, and the cooperativity of both AMP and Mg2+ is abolished or decreased. These structures demonstrate the Q32R mutation affects the conformations of both N-terminal residues and the dynamic loop 52–72. Also importantly, structural comparison indicates that this mutation in helix α2 is detrimental to the R-to-T conversion as evidenced by the absence of quaternary structural changes upon AMP binding, providing direct evidence for the critical role of helix α2 in the allosteric signal transduction.
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Affiliation(s)
- Rong Shi
- Laboratory of Molecular Endocrinology and Oncology, Centre Hospitalier Université de Québec Research Center (CHUQ-CHUL), Department of Molecular Medicine and PROTEO, Laval University, Québec City, Canada
- Département de Biochimie, de Microbiologie et de Bio-Informatique, IBIS et PROTEO, Université Laval, Pavillon Charles-Eugène Marchand, Québec City, Canada
| | - Ze-Yong Chen
- The Laboratory of Structural Biology for Visiting Scientists at Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Shanghai, China
| | - Dao-Wei Zhu
- Département de Biochimie, de Microbiologie et de Bio-Informatique, IBIS et PROTEO, Université Laval, Pavillon Charles-Eugène Marchand, Québec City, Canada
| | - Chunmin Li
- Laboratory of Molecular Endocrinology and Oncology, Centre Hospitalier Université de Québec Research Center (CHUQ-CHUL), Department of Molecular Medicine and PROTEO, Laval University, Québec City, Canada
| | - Yufei Shan
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Shanghai, China
| | - Genjun Xu
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Shanghai, China
| | - Sheng-Xiang Lin
- Laboratory of Molecular Endocrinology and Oncology, Centre Hospitalier Université de Québec Research Center (CHUQ-CHUL), Department of Molecular Medicine and PROTEO, Laval University, Québec City, Canada
- The Laboratory of Structural Biology for Visiting Scientists at Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Shanghai, China
- * E-mail:
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4
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Gao Y, Iancu CV, Mukind S, Choe JY, Honzatko RB. Mechanism of displacement of a catalytically essential loop from the active site of mammalian fructose-1,6-bisphosphatase. Biochemistry 2013; 52:5206-16. [PMID: 23844654 PMCID: PMC4869526 DOI: 10.1021/bi400532n] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AMP triggers a 15° subunit-pair rotation in fructose-1,6-bisphosphatase (FBPase) from its active R state to its inactive T state. During this transition, a catalytically essential loop (residues 50-72) leaves its active (engaged) conformation. Here, the structures of Ile(10) → Asp FBPase and molecular dynamic simulations reveal factors responsible for loop displacement. The AMP/Mg(2+) and AMP/Zn(2+) complexes of Asp(10) FBPase are in intermediate quaternary conformations (completing 12° of the subunit-pair rotation), but the complex with Zn(2+) provides the first instance of an engaged loop in a near-T quaternary state. The 12° subunit-pair rotation generates close contacts involving the hinges (residues 50-57) and hairpin turns (residues 58-72) of the engaged loops. Additional subunit-pair rotation toward the T state would make such contacts unfavorable, presumably causing displacement of the loop. Targeted molecular dynamics simulations reveal no steric barriers to subunit-pair rotations of up to 14° followed by the displacement of the loop from the active site. Principal component analysis reveals high-amplitude motions that exacerbate steric clashes of engaged loops in the near-T state. The results of the simulations and crystal structures are in agreement: subunit-pair rotations just short of the canonical T state coupled with high-amplitude modes sterically displace the dynamic loop from the active site.
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Affiliation(s)
- Yang Gao
- Department of Biochemistry, Biophysics, and Molecular Biology, 4206 Molecular Biology Building, Iowa State University, Ames, Iowa 50011-3260, United States
| | | | | | | | - Richard B. Honzatko
- Department of Biochemistry, Biophysics, and Molecular Biology, 4206 Molecular Biology Building, Iowa State University, Ames, Iowa 50011-3260, United States
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5
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Gizak A, Maciaszczyk E, Dzugaj A, Eschrich K, Rakus D. Evolutionary conserved N-terminal region of human muscle fructose 1,6-bisphosphatase regulates its activity and the interaction with aldolase. Proteins 2008; 72:209-16. [PMID: 18214967 DOI: 10.1002/prot.21909] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
N-terminal residues of muscle fructose 1,6-bisphosphatase (FBPase) are highly conserved among vertebrates. In this article, we present evidence that the conservation is responsible for the unique properties of the muscle FBPase isozyme: high sensitivity to AMP and Ca(2+) inhibition and the high affinity to muscle aldolase, which is a factor desensitizing muscle FBPase toward AMP and Ca(2+). The first N-terminal residue affecting the affinity of muscle FBPase to aldolase is arginine 3. On the other hand, the first residue significantly influencing the kinetics of muscle FBPase is proline 5. Truncation from 5-7 N-terminal residues of the enzyme not only decreases its affinity to aldolase but also reduces its k-(cat) and activation by Mg(2+), and desensitizes FBPase to inhibition by AMP and calcium ions. Deletion of the first 10 amino acids of muscle FBPase abolishes cooperativity of Mg(2+) activation and results in biphasic inhibition of the enzyme by AMP. Moreover, this truncation lowers affinity of muscle FBPase to aldolase about 14 times, making it resemble the liver isozyme. We suggest that the existence of highly AMP-sensitive muscle-like FBPase, activity of which is regulated by metabolite-dependent interaction with aldolase enables the precise regulation of muscle energy expenditures and might contributed to the evolutionary success of vertebrates.
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Affiliation(s)
- Agnieszka Gizak
- Department of Animal Physiology, Institute of Zoology, Wroclaw University, Wroclaw, Poland
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6
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Hines JK, Kruesel CE, Fromm HJ, Honzatko RB. Structure of inhibited fructose-1,6-bisphosphatase from Escherichia coli: distinct allosteric inhibition sites for AMP and glucose 6-phosphate and the characterization of a gluconeogenic switch. J Biol Chem 2007; 282:24697-706. [PMID: 17567577 DOI: 10.1074/jbc.m703580200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Allosteric activation of fructose-1,6-bisphosphatase (FBPase) from Escherichia coli by phosphoenolpyruvate implies rapid feed-forward activation of gluconeogenesis in heterotrophic bacteria. But how do such bacteria rapidly down-regulate an activated FBPase in order to avoid futile cycling? Demonstrated here is the allosteric inhibition of E. coli FBPase by glucose 6-phosphate (Glc-6-P), the first metabolite produced upon glucose transport into the cell. FBPase undergoes a quaternary transition from the canonical R-state to a T-like state in response to Glc-6-P and AMP ligation. By displacing Phe(15), AMP binds to an allosteric site comparable with that of mammalian FBPase. Relative movements in helices H1 and H2 perturb allosteric activator sites for phosphoenolpyruvate. Glc-6-P binds to allosteric sites heretofore not observed in previous structures, perturbing subunits that in pairs form complete active sites of FBPase. Glc-6-P and AMP are synergistic inhibitors of E. coli FBPase, placing AMP/Glc-6-P inhibition in bacteria as a possible evolutionary predecessor to AMP/fructose 2,6-bisphosphate inhibition in mammalian FBPases. With no exceptions, signature residues of allosteric activation appear in bacterial sequences along with key residues of the Glc-6-P site. FBPases in such organisms may be components of metabolic switches that allow rapid changeover between gluconeogenesis and glycolysis in response to nutrient availability.
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Affiliation(s)
- Justin K Hines
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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7
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Hines JK, Fromm HJ, Honzatko RB. Novel allosteric activation site in Escherichia coli fructose-1,6-bisphosphatase. J Biol Chem 2006; 281:18386-93. [PMID: 16670087 DOI: 10.1074/jbc.m602553200] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fructose-1,6-bisphosphatase (FBPase) governs a key step in gluconeogenesis, the conversion of fructose 1,6-bisphosphate into fructose 6-phosphate. In mammals, the enzyme is subject to metabolic regulation, but regulatory mechanisms of bacterial FBPases are not well understood. Presented here is the crystal structure (resolution, 1.45A) of recombinant FBPase from Escherichia coli, the first structure of a prokaryotic Type I FBPase. The E. coli enzyme is a homotetramer, but in a quaternary state between the canonical R- and T-states of porcine FBPase. Phe(15) and residues at the C-terminal side of the first alpha-helix (helix H1) occupy the AMP binding pocket. Residues at the N-terminal side of helix H1 hydrogen bond with sulfate ions buried at a subunit interface, which in porcine FBPase undergoes significant conformational change in response to allosteric effectors. Phosphoenolpyruvate and sulfate activate E. coli FBPase by at least 300%. Key residues that bind sulfate anions are conserved among many heterotrophic bacteria, but are absent in FBPases of organisms that employ fructose 2,6-bisphosphate as a regulator. These observations suggest a new mechanism of regulation in the FBPase enzyme family: anionic ligands, most likely phosphoenolpyruvate, bind to allosteric activator sites, which in turn stabilize a tetramer and a polypeptide fold that obstructs AMP binding.
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Affiliation(s)
- Justin K Hines
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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8
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Dzugaj A. Localization and regulation of muscle fructose-1,6-bisphosphatase, the key enzyme of glyconeogenesis. ACTA ACUST UNITED AC 2006; 46:51-71. [PMID: 16857246 DOI: 10.1016/j.advenzreg.2006.01.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Andrzej Dzugaj
- Department of Animal Physiology, Wroclaw University, Wroclaw, Poland
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9
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Rakus D, Maciaszczyk E, Wawrzycka D, Ułaszewski S, Eschrich K, Dzugaj A. The origin of the high sensitivity of muscle fructose 1,6-bisphosphatase towards AMP. FEBS Lett 2005; 579:5577-81. [PMID: 16213487 DOI: 10.1016/j.febslet.2005.09.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2005] [Revised: 07/13/2005] [Accepted: 09/13/2005] [Indexed: 11/27/2022]
Abstract
Adenosine 5'-monophosphate (AMP) inhibits muscle fructose 1,6-bisphosphatase (FBPase) about 44 times stronger than the liver isozyme. The key role in strong AMP binding to muscle isozyme play K20, T177 and Q179. Muscle FBPase which has been mutated towards the liver enzyme (K20E/T177M/Q179C) is inhibited by AMP about 26 times weaker than the wild-type muscle enzyme, but it binds the fluorescent AMP analogue, 2',3'-O-(2,4,6-trinitrophenyl)adenosine 5'-monophosphate (TNP-AMP), similarly to the wild-type liver enzyme. The reverse mutation of liver FBPase towards the muscle isozyme significantly increases the affinity of the mutant to TNP-AMP. High affinity to the inhibitor but low sensitivity to AMP of the liver triple mutant suggest differences between the isozymes in the mechanism of allosteric signal transmission.
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Affiliation(s)
- D Rakus
- Department of Animal Physiology, Institute of Zoology, Wroclaw University, Poland
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10
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Iancu CV, Mukund S, Fromm HJ, Honzatko RB. R-state AMP complex reveals initial steps of the quaternary transition of fructose-1,6-bisphosphatase. J Biol Chem 2005; 280:19737-45. [PMID: 15767255 DOI: 10.1074/jbc.m501011200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
AMP transforms fructose-1,6-bisphosphatase from its active R-state to its inactive T-state; however, the mechanism of that transformation is poorly understood. The mutation of Ala(54) to leucine destabilizes the T-state of fructose-1,6-bisphosphatase. The mutant enzyme retains wild-type levels of activity, but the concentration of AMP that causes 50% inhibition increases 50-fold. In the absence of AMP, the Leu(54) enzyme adopts an R-state conformation nearly identical to that of the wild-type enzyme. The mutant enzyme, however, grows in two crystal forms in the presence of saturating AMP. In one form, the AMP-bound tetramer is in a T-like conformation, whereas in the other form, the AMP-bound tetramer is in a R-like conformation. The latter reveals conformational changes in two helices due to the binding of AMP. Helix H1 moves toward the center of the tetramer and displaces Ile(10) from a hydrophobic pocket. The displacement of Ile(10) exposes a hydrophobic surface critical to interactions that stabilize the T-state. Helix H2 moves away from the center of the tetramer, breaking hydrogen bonds with a buried loop (residues 187-195) in an adjacent subunit. The same hydrogen bonds reform but only after the quaternary transition to the T-state. Proposed here is a model that accounts for the quaternary transition and cooperativity in the inhibition of catalysis by AMP.
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Affiliation(s)
- Cristina V Iancu
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, 50011, USA
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Nelson SW, Honzatko RB, Fromm HJ. Origin of cooperativity in the activation of fructose-1,6-bisphosphatase by Mg2+. J Biol Chem 2004; 279:18481-7. [PMID: 14978036 DOI: 10.1074/jbc.m308811200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fructose-1,6-bisphosphatase requires a divalent metal cation for catalysis, Mg(2+) being its most studied activator. Phosphatase activity increases sigmoidally with the concentration of Mg(2+), but the mechanistic basis for such cooperativity is unknown. Bound magnesium cations can interact within a single subunit or between different subunits of the enzyme tetramer. Mutations of Asp(118), Asp(121), or Glu(97) to alanine inactivate the recombinant porcine enzyme. These residues bind directly to magnesium cations at the active site. Three different hybrid tetramers of fructose-1,6-bisphosphatase, composed of one wild-type subunit and three subunits bearing one of the mutations above, exhibit kinetic parameters (K(m) for fructose-1,6-bisphosphate, 1.1-1.8 microm; K(a) for Mg(2+), 0.34-0.76 mm; K(i) for fructose-2,6-bisphosphate, 0.11-0.61 microm; and IC(50) for AMP, 3.8-7.4 microm) nearly identical to those of the wild-type enzyme. Notwithstanding these similarities, the k(cat) parameter for each hybrid tetramer is approximately one-fourth of that for the wild-type enzyme. Evidently, each subunit in the wild-type tetramer can independently achieve maximum velocity when activated by Mg(2+). Moreover, the activities of the three hybrid tetramers vary sigmoidally with the concentration of Mg(2+) (Hill coefficients of approximately 2). The findings above are fully consistent with a mechanism of cooperativity that arises from within a single subunit of fructose-1,6-bisphosphatase.
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Affiliation(s)
- Scott W Nelson
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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12
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Choe JY, Nelson SW, Arienti KL, Axe FU, Collins TL, Jones TK, Kimmich RDA, Newman MJ, Norvell K, Ripka WC, Romano SJ, Short KM, Slee DH, Fromm HJ, Honzatko RB. Inhibition of fructose-1,6-bisphosphatase by a new class of allosteric effectors. J Biol Chem 2003; 278:51176-83. [PMID: 14530289 DOI: 10.1074/jbc.m308396200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A highly constrained pseudo-tetrapeptide (OC252-324) further defines a new allosteric binding site located near the center of fructose-1,6-bisphosphatase. In a crystal structure, pairs of inhibitory molecules bind to opposite faces of the enzyme tetramer. Each ligand molecule is in contact with three of four subunits of the tetramer, hydrogen bonding with the side chain of Asp187 and the backbone carbonyl of residue 71, and electrostatically interacting with the backbone carbonyl of residue 51. The ligated complex adopts a quaternary structure between the canonical R- and T-states of fructose-1,6-bisphosphatase, and yet a dynamic loop essential for catalysis (residues 52-72) is in a conformation identical to that of the T-state enzyme. Inhibition by the pseudo-tetrapeptide is cooperative (Hill coefficient of 2), synergistic with both AMP and fructose 2,6-bisphosphate, noncompetitive with respect to Mg2+, and uncompetitive with respect to fructose 1,6-bisphosphate. The ligand dramatically lowers the concentration at which substrate inhibition dominates the kinetics of fructose-1,6-bisphosphatase. Elevated substrate concentrations employed in kinetic screens may have facilitated the discovery of this uncompetitive inhibitor. Moreover, the inhibitor could mimic an unknown natural effector of fructose-1,6-bisphosphatase, as it interacts strongly with a conserved residue of undetermined functional significance.
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Affiliation(s)
- Jun-Young Choe
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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13
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Choe JY, Nelson SW, Fromm HJ, Honzatko RB. Interaction of Tl+ with product complexes of fructose-1,6-bisphosphatase. J Biol Chem 2003; 278:16008-14. [PMID: 12595529 DOI: 10.1074/jbc.m212394200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fructose-1,6-bisphosphatase requires divalent cations (Mg2+, Mn2+, or Zn2+) for catalysis, but a diverse set of monovalent cations (K+, Tl+, Rb+, or NH(4)(+)) will further enhance enzyme activity. Here, the interaction of Tl+ with fructose-1,6-bisphosphatase is explored under conditions that support catalysis. On the basis of initial velocity kinetics, Tl+ enhances catalysis by 20% with a K(a) of 1.3 mm and a Hill coefficient near unity. Crystal structures of enzyme complexes with Mg2+, Tl+, and reaction products, in which the concentration of Tl+ is 1 mm or less, reveal Mg2+ at metal sites 1, 2, and 3 of the active site, but little or no bound Tl+. Intermediate concentrations of Tl+ (5-20 mm) displace Mg2+ from site 3 and the 1-OH group of fructose 6-phosphate from in-line geometry with respect to bound orthophosphate. Loop 52-72 appears in a new conformational state, differing from its engaged conformation by disorder in residues 61-69. Tl+ does not bind to metal sites 1 or 2 in the presence of Mg2+, but does bind to four other sites with partial occupancy. Two of four Tl+ sites probably represent alternative binding sites for the site 3 catalytic Mg2+, whereas the other sites could play roles in monovalent cation activation.
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Affiliation(s)
- Jun-Yong Choe
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, IA 50011, USA
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14
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Rakus D, Tillmann H, Wysocki R, Ulaszewski S, Eschrich K, Dzugaj A. Different sensitivities of mutants and chimeric forms of human muscle and liver fructose-1,6-bisphosphatases towards AMP. Biol Chem 2003; 384:51-8. [PMID: 12674499 DOI: 10.1515/bc.2003.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AMP is an allosteric inhibitor of human muscle and liver fructose-1,6-bisphosphatase (FBPase). Despite strong similarity of the nucleotide binding domains, the muscle enzyme is inhibited by AMP approximately 35 times stronger than liver FBPase: I0.5 for muscle and for liver FBPase are 0.14 microM and 4.8 microM, respectively. Chimeric human muscle (L50M288) and chimeric human liver enzymes (M50L288), in which the N-terminal residues (1-50) were derived from the human liver and human muscle FBPases, respectively, were inhibited by AMP 2-3 times stronger than the wild-type liver enzyme. An amino acid exchange within the N-terminal region of the muscle enzyme towards liver FBPase (Lys20-->Glu) resulted in 13-fold increased I0.5 values compared to the wild-type muscle enzyme. However, the opposite exchanges in the liver enzyme (Glu20-->Lys and double mutation Glu19-->Asp/Glu20-->Lys) did not change the sensitivity for AMP inhibition of the liver mutant (I0.5 value of 4.9 microM). The decrease of sensitivity for AMP of the muscle mutant Lys20-->Glu, as well as the lack of changes in the inhibition by AMP of liver mutants Glu20-->Lys and Glu19-->Asp/Glu20-->Lys, suggest a different mechanism of AMP binding to the muscle and liver enzyme.
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Affiliation(s)
- Dariusz Rakus
- Department of Animal Physiology, Zoological Institute, Wroclaw University, Cybulskiego 30, 50-205 Wroclaw, Poland
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15
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Nelson SW, Honzatko RB, Fromm HJ. Hybrid tetramers of porcine liver fructose-1,6-bisphosphatase reveal multiple pathways of allosteric inhibition. J Biol Chem 2002; 277:15539-45. [PMID: 11854289 DOI: 10.1074/jbc.m112304200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fructose-1,6-bisphosphatase is a square planar tetramer of identical subunits, which exhibits cooperative allosteric inhibition of catalysis by AMP. Protocols for in vitro subunit exchange provide three of five possible hybrid tetramers of fructose-1,6-bisphosphatase in high purity. The two hybrid types with different subunits in the top and bottom halves of the tetramer co-purify. Hybrid tetramers, formed from subunits unable to bind AMP and subunits with wild-type properties, differ from the wild-type enzyme only in regard to their properties of AMP inhibition. Hybrid tetramers exhibit cooperative, potent, and complete (100%) AMP inhibition if at least one functional AMP binding site exists in the top and bottom halves of the tetramer. Furthermore, titrations of hybrid tetramers with AMP, monitored by a tryptophan reporter group, reveal cooperativity and fluorescence changes consistent with an R- to T-state transition, provided that again at least one functional AMP site exists in the top and bottom halves of the tetramer. In contrast, hybrid tetramers, which have functional AMP binding sites in only one half (top/bottom), exhibit an R- to T-state transition and complete AMP inhibition, but without cooperativity. Evidently, two pathways of allosteric inhibition of fructose-1,6-bisphosphatase are possible, only one of which is cooperative.
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Affiliation(s)
- Scott W Nelson
- Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011, USA
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