51
|
Forbes GC, Kennedy AR, Mulvey RE, Roberts BA, Rowlings RB. Alkali Metal Cation−π Interactions Stabilized Solely by [M{N(SiMe3)2}3]- Anions (M = Mg or Zn): The Competing Influence of Alkali Metal···C(Me) Agostic Interactions. Organometallics 2002. [DOI: 10.1021/om020596u] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Glenn C. Forbes
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, Scotland
| | - Alan R. Kennedy
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, Scotland
| | - Robert E. Mulvey
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, Scotland
| | - Brett A. Roberts
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, Scotland
| | - René B. Rowlings
- Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XL, Scotland
| |
Collapse
|
52
|
Gokel GW, Barbour LJ, Ferdani R, Hu J. Lariat ether receptor systems show experimental evidence for alkali metal cation-pi interactions. Acc Chem Res 2002; 35:878-86. [PMID: 12379140 DOI: 10.1021/ar000093p] [Citation(s) in RCA: 184] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cation-pi interactions occur between cations and electron-rich species such as double bonds, triple bonds, and arenes. The pi-electron system may be neutral or anionic, but the latter are less relevant to biology, at least so far as is currently known. Among the 20 essential amino acids, there are four aromatic residues. These are benzene, phenol, indole, and imidazole, on the side chains of phenylalanine, tyrosine, tryptophan, and histidine, respectively. Of these, imidazole is expected to be a sigma-donor, and benzene, phenol, and indole are antipicated to serve as pi-donors. Sodium and potassium are the most abundant cations in living systems. This Account describes an experimental system that has been developed to probe, especially by X-ray crystallography, the interactions that occur between Na(+) or K(+) and the neutral arenes of particular biological significance.
Collapse
Affiliation(s)
- George W Gokel
- Division of Bioorganic Chemistry, Bioorganic Chemistry Program, and Department of Molecular Biology & Pharmacology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
| | | | | | | |
Collapse
|
53
|
Hu J, Barbour LJ, Gokel GW. The indole side chain of tryptophan as a versatile pi-donor. J Am Chem Soc 2002; 124:10940-1. [PMID: 12224916 DOI: 10.1021/ja020586k] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Single-armed, 15- and 18-membered lariat ether receptor systems having indolylethyl side arms bind Na+ and K+ in the ring. The indole residue serves as a pi-donor to the ring-bound cation. Whether the five- or six-membered ring interacts most directly with Na+ or K+ depends on whether the sidearm is attached to indole's 3- or 5-position. This suggests that structural as well as electronic factors are important in pi-complexation of alkali metal cations.
Collapse
Affiliation(s)
- Jiaxin Hu
- Division of Bioorganic Chemistry, Bioorganic Chemistry Program, and Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110, USA
| | | | | |
Collapse
|
54
|
Hall DR, Bond CS, Leonard GA, Watt CI, Berry A, Hunter WN. Structure of tagatose-1,6-bisphosphate aldolase. Insight into chiral discrimination, mechanism, and specificity of class II aldolases. J Biol Chem 2002; 277:22018-24. [PMID: 11940603 DOI: 10.1074/jbc.m202464200] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tagatose-1,6-bisphosphate aldolase (TBPA) is a tetrameric class II aldolase that catalyzes the reversible condensation of dihydroxyacetone phosphate with glyceraldehyde 3-phosphate to produce tagatose 1,6-bisphosphate. The high resolution (1.45 A) crystal structure of the Escherichia coli enzyme, encoded by the agaY gene, complexed with phosphoglycolohydroxamate (PGH) has been determined. Two subunits comprise the asymmetric unit, and a crystallographic 2-fold axis generates the functional tetramer. A complex network of hydrogen bonds position side chains in the active site that is occupied by two cations. An unusual Na+ binding site is created using a pi interaction with Tyr183 in addition to five oxygen ligands. The catalytic Zn2+ is five-coordinate using three histidine nitrogens and two PGH oxygens. Comparisons of TBPA with the related fructose-1,6-bisphosphate aldolase (FBPA) identifies common features with implications for the mechanism. Because the major product of the condensation catalyzed by the enzymes differs in the chirality at a single position, models of FBPA and TBPA with their cognate bisphosphate products provide insight into chiral discrimination by these aldolases. The TBPA active site is more open on one side than FBPA, and this contributes to a less specific enzyme. The availability of more space and a wider range of aldehyde partners used by TBPA together with the highly specific nature of FBPA suggest that TBPA might be a preferred enzyme to modify for use in biotransformation chemistry.
Collapse
Affiliation(s)
- David R Hall
- Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
| | | | | | | | | | | |
Collapse
|
55
|
Hu J, Barbour LJ, Gokel GW. Probing alkali metal-pi interactions with the side chain residue of tryptophan. Proc Natl Acad Sci U S A 2002; 99:5121-6. [PMID: 11943874 PMCID: PMC122732 DOI: 10.1073/pnas.082645599] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Feeble forces play a significant role in the organization of proteins. These include hydrogen bonding, hydrophobic interactions, salt bridge formation, and steric interactions. The alkali metal cation-pi interaction is a force of potentially profound importance but its consideration in biology has been limited by the lack of experimental evidence. Our previous studies of cation-pi interactions with Na(+) and K(+) involved the side arms of tryptophan (indole), tyrosine (phenol), and phenylalanine (benzene) as the arene donors. The receptor system possesses limiting steric constraints. In this report, we show that direct interactions between alkali metals and arenes occur at or within the van der Waals contact distance.
Collapse
Affiliation(s)
- Jiaxin Hu
- Program in Bioorganic Chemistry, Division of Bioorganic Chemistry, Department of Molecular Biology and Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110, USA
| | | | | |
Collapse
|
56
|
Abstract
Cation-pi interactions are increasingly recognized as important in chemistry and biology. Here we investigate the cation-pi interaction by determining its effect on the helicity of model peptides using a combination of CD and NMR spectroscopy. The data show that a single Trp/Arg interaction on the surface of a peptide can make a significant net favorable free energy contribution to helix stability if the two residues are positioned with appropriate spacing and orientation. The solvent-exposed Trp-->Arg (i, i + 4) interaction in helices can contribute -0.4 kcal/mol to the helix stability, while no free energy gain is detected if the two residues have the reversed orientation, Arg-->Trp (i, i + 4). The derived free energy is consistent with other experimental results studied in proteins or model peptides on cation-pi interactions. However in the same system the postulated Phe/Arg (i, i + 4) cation-pi interaction provides no net free energy to helix stability. Thus the Trp-->Arg interaction is stronger than Phe-->Arg. The cation-pi interactions are not sensitive to the screening effect by adding neutral salt as indicated by salt titration. Our results are in qualitative agreement with theoretical calculations emphasizing that cation-pi interactions can contribute significantly to protein stability with the order Trp > Phe. However, our and other experimental values are significantly smaller than estimates from theoretical calculations.
Collapse
Affiliation(s)
- Zhengshuang Shi
- Department of Chemistry, New York University, New York 10003, USA
| | | | | |
Collapse
|
57
|
Gokel GW, Barbour LJ, De Wall SL, Meadows ES. Macrocyclic polyethers as probes to assess and understand alkali metal cation-π interactions. Coord Chem Rev 2001. [DOI: 10.1016/s0010-8545(01)00380-0] [Citation(s) in RCA: 131] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
58
|
Jian Tan X, Liang Zhu W, Cui M, Min Luo X, De Gu J, Silman I, Sussman JL, Liang Jiang H, Yun Ji R, Xian Chen K. Noncovalent interaction or chemical bonding between alkaline earth cations and benzene? A quantum chemistry study using MP2 and density-functional theory methods. Chem Phys Lett 2001. [DOI: 10.1016/s0009-2614(01)01176-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
|
59
|
Hu J, Barbour LJ, Ferdani R, Gokel GW. Solid state network formation in arene-Sidearmed lariat ether complexes: contrasting behavior of sodium, potassium, and calcium cation complexes. ACTA ACUST UNITED AC 2001. [DOI: 10.1016/s1472-7862(02)00008-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
60
|
Siu FM, Ma NL, Tsang CW. Cation-pi interactions in sodiated phenylalanine complexes: is phenylalanine in the charge-solvated or zwitterionic form? J Am Chem Soc 2001; 123:3397-8. [PMID: 11457088 DOI: 10.1021/ja0056872] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- F M Siu
- Department of Applied Biology and Chemical Technology Hong Kong Polytechnic University Hung Hom, Hong Kong, P. R. China
| | | | | |
Collapse
|
61
|
Meadows ES, De Wall SL, Barbour LJ, Gokel GW. Alkali metal cation-pi interactions observed by using a lariat ether model system. J Am Chem Soc 2001; 123:3092-107. [PMID: 11457020 DOI: 10.1021/ja003059e] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Na(+) or K(+) cation-pi interaction has been experimentally probed by using synthetic receptors that comprise diaza-18-crown-6 lariat ethers having ethylene sidearms attached to aromatic pi-donors. The side chains are 2-(3-indolyl)ethyl (7), 2-(3-(1-methyl)indolyl)ethyl (8), 2-(3-(5-methoxy)indolyl)ethyl (9), 2-(4-hydroxyphenyl)ethyl (10), 2-phenylethyl (11), 2-pentafluorophenylethyl (12), and 2-(1-naphthyl)ethyl (13). Solid-state structures are reported for six examples of alkali metal complexes in which the cation is pi-coordinated by phenyl, phenol, or indole. Indole-containing crown, 7, adopts a similar conformation when bound by NaI, KI, KSCN, or KPF(6). In each case, the macroring and both arenes coordinate the cation; the counteranion is excluded from the solvation sphere. NMR measurements in acetone-d(6) solution confirm the observed solid-state conformations of unbound 7 and 7.NaI. In 7.Na(+) and 7.K(+), the pyrrolo, rather than benzo, subunit of indole is the pi-donor for the alkali metal cation. Cation-pi complexes were also observed for 10.KI and11.KI. In these cases, the orientation of the cation on the aromatic ring is in accord with the binding site predicted by computational studies. In contrast to the phenyl case (11) the pentafluorophenyl group of 12 failed to coordinate K(+). Solid-state structures are also reported for 7.NaPF(6), 10.NaI, 11.NaI, 13.KI, 13.KPF(6), and 9.NaI, in which cation-pi complexation is not observed. Steric and electrostatic considerations in the pi-complexation of alkali metal cations by these lariat ethers are thought to account for the observed complexation behavior or lack thereof.
Collapse
Affiliation(s)
- E S Meadows
- Bioorganic Chemistry Program and Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110
| | | | | | | |
Collapse
|
62
|
Amino Acids, Peptides, and Proteins. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50005-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
63
|
Silverman WR, Tang CY, Mock AF, Huh KB, Papazian DM. Mg(2+) modulates voltage-dependent activation in ether-à-go-go potassium channels by binding between transmembrane segments S2 and S3. J Gen Physiol 2000; 116:663-78. [PMID: 11055995 PMCID: PMC2229486 DOI: 10.1085/jgp.116.5.663] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Extracellular Mg(2+) directly modulates voltage-dependent activation in ether-à-go-go (eag) potassium channels, slowing the kinetics of ionic and gating currents (Tang, C.-Y., F. Bezanilla, and D.M. Papazian. 2000. J. Gen. Physiol. 115:319-337). To exert its effect, Mg(2+) presumably binds to a site in or near the eag voltage sensor. We have tested the hypothesis that acidic residues unique to eag family members, located in transmembrane segments S2 and S3, contribute to the Mg(2+)-binding site. Two eag-specific acidic residues and three acidic residues found in the S2 and S3 segments of all voltage-dependent K(+) channels were individually mutated in Drosophila eag, mutant channels were expressed in Xenopus oocytes, and the effect of Mg(2+) on ionic current kinetics was measured using a two electrode voltage clamp. Neutralization of eag-specific residues D278 in S2 and D327 in S3 eliminated Mg(2+)-sensitivity and mimicked the slowing of activation kinetics caused by Mg(2+) binding to the wild-type channel. These results suggest that Mg(2+) modulates activation kinetics in wild-type eag by screening the negatively charged side chains of D278 and D327. Therefore, these residues are likely to coordinate the bound ion. In contrast, neutralization of the widely conserved residues D284 in S2 and D319 in S3 preserved the fast kinetics seen in wild-type eag in the absence of Mg(2+), indicating that D284 and D319 do not mediate the slowing of activation caused by Mg(2+) binding. Mutations at D284 affected the eag gating pathway, shifting the voltage dependence of Mg(2+)-sensitive, rate limiting transitions in the hyperpolarized direction. Another widely conserved residue, D274 in S2, is not required for Mg(2+) sensitivity but is in the vicinity of the binding site. We conclude that Mg(2+) binds in a water-filled pocket between S2 and S3 and thereby modulates voltage-dependent gating. The identification of this site constrains the packing of transmembrane segments in the voltage sensor of K(+) channels, and suggests a molecular mechanism by which extracellular cations modulate eag activation kinetics.
Collapse
Affiliation(s)
- William R. Silverman
- Department of Physiology and Molecular Biology Institute, University of California Los Angeles School of Medicine, Los Angeles, California 90095-1751
| | - Chih-Yung Tang
- Department of Physiology and Molecular Biology Institute, University of California Los Angeles School of Medicine, Los Angeles, California 90095-1751
| | - Allan F. Mock
- Department of Physiology and Molecular Biology Institute, University of California Los Angeles School of Medicine, Los Angeles, California 90095-1751
| | - Kyung-Bong Huh
- Department of Physiology and Molecular Biology Institute, University of California Los Angeles School of Medicine, Los Angeles, California 90095-1751
| | - Diane M. Papazian
- Department of Physiology and Molecular Biology Institute, University of California Los Angeles School of Medicine, Los Angeles, California 90095-1751
| |
Collapse
|
64
|
Wintjens R, Liévin J, Rooman M, Buisine E. Contribution of cation-pi interactions to the stability of protein-DNA complexes. J Mol Biol 2000; 302:395-410. [PMID: 10970741 DOI: 10.1006/jmbi.2000.4040] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cation-pi interactions between an aromatic ring and a positive charge located above it have proven to be important in protein structures and biomolecule associations. Here, the role of these interactions at the interface of protein-DNA complexes is investigated, by means of ab initio quantum mechanics energy calculations and X-ray structure analyses. Ab initio energy calculations indicate that Na ions and DNA bases can form stable cation-pi complexes, whose binding strength strongly depends on the type of base, on the position of the Na ion, and whether the base is isolated or included in a double-stranded B-DNA. A survey of protein-DNA complex structures using appropriate geometrical criteria revealed cation-pi interactions in 71% of the complexes. More than half of the cation-pi pairs involve arginine residues, about one-third asparagine or glutamine residues that only carry a partial charge, and one-seventh lysine residues. The most frequently observed pair, which is also the most stable as monitored by ab initio energy calculations, is arginine- guanine. Arginine-adenine interactions are also favorable in general, although to a lesser extent, whereas those with thymine and cytosine are not. Our calculations show that the major contribution to cation-pi interactions with DNA bases is of electrostatic nature. These interactions often occur concomitantly with hydrogen bonds with adjacent bases; their strength is estimated to be from three to four times lower than that of hydrogen bonds. Finally, the role of cation-pi interactions in the stability and specificity of protein-DNA complexes is discussed.
Collapse
Affiliation(s)
- R Wintjens
- UMR 8525 CNRS-Université de Lille II, Institut de Biologie de Lille, Institut Pasteur de Lille, 1 rue du Professeur Calmette, BP 447, 59021 Lille cédex, France
| | | | | | | |
Collapse
|
65
|
|
66
|
Barbour LJ, De Wall SL, Meadows ES, Gokel GW. Experimental Evidence for Alkali-Metal Ion Cation−π Interactions Using Bibracchial Lariat Ether Complexes. Ind Eng Chem Res 2000. [DOI: 10.1021/ie990780o] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Leonard J. Barbour
- Bioorganic Chemistry Program and Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 S. Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110, and Department of Chemistry, University of Missouri, 601 S. College Avenue, Columbia, Missouri 65211
| | - Stephen L. De Wall
- Bioorganic Chemistry Program and Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 S. Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110, and Department of Chemistry, University of Missouri, 601 S. College Avenue, Columbia, Missouri 65211
| | - Eric S. Meadows
- Bioorganic Chemistry Program and Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 S. Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110, and Department of Chemistry, University of Missouri, 601 S. College Avenue, Columbia, Missouri 65211
| | - George W. Gokel
- Bioorganic Chemistry Program and Department of Molecular Biology & Pharmacology, Washington University School of Medicine, 660 S. Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110, and Department of Chemistry, University of Missouri, 601 S. College Avenue, Columbia, Missouri 65211
| |
Collapse
|
67
|
De Wall SL, Meadows ES, Barbour LJ, Gokel GW. Synthetic receptors as models for alkali metal cation-pi binding sites in proteins. Proc Natl Acad Sci U S A 2000; 97:6271-6. [PMID: 10841532 PMCID: PMC18592 DOI: 10.1073/pnas.97.12.6271] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The alkali metal cations Na(+) and K(+) have several important physiological roles, including modulating enzyme activity. Recent work has suggested that alkali metal cations may be coordinated by pi systems, such as the aromatic amino acid side chains. The ability of K(+) to interact with an aromatic ring has been assessed by preparing a family of synthetic receptors that incorporate the aromatic side chains of phenylalanine, tyrosine, and tryptophan. These receptors are constructed around a diaza-18-crown-6 scaffold, which serves as the primary binding site for an alkali metal cation. The ability of the aromatic rings to coordinate a cation was determined by crystallizing each of the receptors in the presence of K(+) and by solving the solid state structures. In all cases, complexation of K(+) by the pi system was observed. When possible, the structures of the unbound receptors also were determined for comparison. Further proof that the aromatic ring makes an energetically favorable interaction with the cation was obtained by preparing a receptor in which the arene was perfluorinated. Fluorination of the arene reverses the electrostatics, but the aromaticity is maintained. The fluorinated arene rings do not coordinate the cation in the solid state structure of the K(+) complex. Thus, the results of the predicted electrostatic reversal were confirmed. Finally, the biological implications of the alkali metal cation-pi interaction are addressed.
Collapse
Affiliation(s)
- S L De Wall
- Bioorganic Chemistry Program and Department of Molecular Biology and Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8103, St. Louis, MO 63110, USA
| | | | | | | |
Collapse
|
68
|
Phosphatidylcholine-Preferring Phospholipase C from B. cereus. Function, Structure, and Mechanism. Top Curr Chem (Cham) 2000. [DOI: 10.1007/3-540-45035-1_5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
|
69
|
|
70
|
Abstract
Cation-pi interactions in protein structures are identified and evaluated by using an energy-based criterion for selecting significant sidechain pairs. Cation-pi interactions are found to be common among structures in the Protein Data Bank, and it is clearly demonstrated that, when a cationic sidechain (Lys or Arg) is near an aromatic sidechain (Phe, Tyr, or Trp), the geometry is biased toward one that would experience a favorable cation-pi interaction. The sidechain of Arg is more likely than that of Lys to be in a cation-pi interaction. Among the aromatics, a strong bias toward Trp is clear, such that over one-fourth of all tryptophans in the data bank experience an energetically significant cation-pi interaction.
Collapse
Affiliation(s)
- J P Gallivan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | | |
Collapse
|
71
|
Alvarez M, Wouters J, Maes D, Mainfroid V, Rentier-Delrue F, Wyns L, Depiereux E, Martial JA. Lys13 plays a crucial role in the functional adaptation of the thermophilic triose-phosphate isomerase from Bacillus stearothermophilus to high temperatures. J Biol Chem 1999; 274:19181-7. [PMID: 10383424 DOI: 10.1074/jbc.274.27.19181] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The thermophilic triose-phosphate isomerases (TIMs) of Bacillus stearothermophilus (bTIM) and Thermotoga maritima (tTIM) have been found to possess a His12-Lys13 pair instead of the Asn12-Gly13 pair normally present in mesophilic TIMs. His12 in bTIM was proposed to prevent deamidation at high temperature, while the precise role of Lys13 is unknown. To investigate the role of the His12 and Lys13 pair in the enzyme's thermoadaptation, we reintroduced the "mesophilic residues" Asn and Gly into both thermophilic TIMs. Neither double mutant displayed diminished structural stability, but the bTIM double mutant showed drastically reduced catalytic activity. No similar behavior was observed with the tTIM double mutant, suggesting that the presence of the His12 and Lys13 cannot be systematically correlated to thermoadaptation in TIMs. We determined the crystal structure of the bTIM double mutant complexed with 2-phosphoglycolate to 2.4-A resolution. A molecular dynamics simulation showed that upon substitution of Lys13 to Gly an increase of the flexibility of loop 1 is observed, causing an incorrect orientation of the catalytic Lys10. This suggests that Lys13 in bTIM plays a crucial role in the functional adaptation of this enzyme to high temperature. Analysis of bTIM single mutants supports this assumption.
Collapse
Affiliation(s)
- M Alvarez
- Laboratoire de Biologie Moléculaire et de Génie Génétique, Université de Liège, B6, Sart Tilman, B4000 Liège, Belgium
| | | | | | | | | | | | | | | |
Collapse
|
72
|
Fernández-Recio J, Romero A, Sancho J. Energetics of a hydrogen bond (charged and neutral) and of a cation-pi interaction in apoflavodoxin. J Mol Biol 1999; 290:319-30. [PMID: 10388575 DOI: 10.1006/jmbi.1999.2863] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Anabaena apoflavodoxin contains a single histidine residue (H34) that interacts with two aromatic residues (F7 and Y47). The histidine and phenylalanine rings are almost coplanar and they can establish a cation-pi interaction when the histidine is protonated. The histidine and tyrosine side-chains are engaged in a hydrogen bond, which is their only contact. We analyse the energetics of these interactions using p Ka-shift analysis, double-mutant cycle analysis at two pH values, and X-ray crystallography. The H/F interaction is very weak when the histidine is neutral, but it is strengthened by 0.5 kcal mol-1on histidine protonation. Supporting this fact, the histidine p Kain a F7L mutant is 0.4 pH units lower than in wild-type. The strength of the H/Y hydrogen bond is 0.7 kcal mol-1when the histidine is charged, and it becomes stronger (1.3 kcal mol-1) when the histidine is neutral. This is consistent with our observation that the (H34)Nepsilon2-OH(Y47) distance is slightly shorter in the apoflavodoxin structure at pH 9.0 than in the previously reported structure at pH 6.0. It is also consistent with a histidine p Kavalue 0.6 pH units higher in a Y47F mutant than in the wild-type protein. We suggest that the higher stability of the neutral hydrogen bond could be due to a higher desolvation penalty of the charged hydrogen bond that would offset its more favourable enthalpy of formation. The relationship between hydrogen bond strength and the contribution of hydrogen bonds to protein stability is discussed.
Collapse
Affiliation(s)
- J Fernández-Recio
- Departamento de Bioquímica y Biología Molecular y Celular Facultad de Ciencias, Universidad de Zaragoza, 50009-Zaragoza, Spain
| | | | | |
Collapse
|
73
|
De Wall SL, Meadows ES, Barbour LJ, Gokel GW. Solution- and Solid-State Evidence for Alkali Metal Cation−π Interactions with Indole, the Side Chain of Tryptophan. J Am Chem Soc 1999. [DOI: 10.1021/ja9907921] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stephen L. De Wall
- Bioorganic Chemistry Program and Department of Molecular Biology and Pharmacology Washington University School of Medicine 660 South Euclid Avenue, Campus Box 8103 St. Louis, Missouri 63110 Department of Chemistry, University of Missouri Columbia, Missouri 65211
| | - Eric S. Meadows
- Bioorganic Chemistry Program and Department of Molecular Biology and Pharmacology Washington University School of Medicine 660 South Euclid Avenue, Campus Box 8103 St. Louis, Missouri 63110 Department of Chemistry, University of Missouri Columbia, Missouri 65211
| | - Leonard J. Barbour
- Bioorganic Chemistry Program and Department of Molecular Biology and Pharmacology Washington University School of Medicine 660 South Euclid Avenue, Campus Box 8103 St. Louis, Missouri 63110 Department of Chemistry, University of Missouri Columbia, Missouri 65211
| | - George W. Gokel
- Bioorganic Chemistry Program and Department of Molecular Biology and Pharmacology Washington University School of Medicine 660 South Euclid Avenue, Campus Box 8103 St. Louis, Missouri 63110 Department of Chemistry, University of Missouri Columbia, Missouri 65211
| |
Collapse
|
74
|
Cabarcos OM, Weinheimer CJ, Lisy JM. Size selectivity by cation–π interactions: Solvation of K+ and Na+ by benzene and water. J Chem Phys 1999. [DOI: 10.1063/1.478752] [Citation(s) in RCA: 199] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
|