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Nachman RJ, Moyna G, Williams HJ, Tobe SS, Scott AI. Synthesis, biological activity, and conformational studies of insect allatostatin neuropeptide analogues incorporating turn-promoting moieties. Bioorg Med Chem 1998; 6:1379-88. [PMID: 9784875 DOI: 10.1016/s0968-0896(98)00129-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Allatostatins are 6-18 amino acid peptides synthezed by insects to control production of juvenile hormones, which in turn regulate functions including metamorphosis and egg production. Four insect allatostatin neuropeptide analogues incorporating turn-promoting pseudopeptide moieties in the region responsible for biological activity were prepared by solid phase peptide synthetic methods. Bioassay indicated that activities approached those of the natural neuropeptides, and molecular models based on NMR data showed similar conformations and the presence of a beta-turn in the active core region for the four analogues. Differences in activity are believed to be due to differences in bulk and relative position of atoms in the unnatural portion of the analogues, and their differing degrees of conformational freedom. The studies support the feasibility of development of neuropeptide-based insect control agents resistant to peptidase deactivation.
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Moyna G, Zauhar RJ, Williams HJ, Nachman RJ, Scott AI. Comparison of ring current methods for use in molecular modeling refinement of NMR derived three-dimensional structures. JOURNAL OF CHEMICAL INFORMATION AND COMPUTER SCIENCES 1998; 38:702-9. [PMID: 9691476 DOI: 10.1021/ci980402e] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
A comparison between three different methods commonly used to estimate ring current effects on chemical shifts is presented. Haigh-Mallion, Johnson-Bovey, and classical point-dipole approximations were used to estimate the ring current contribution to chemical shifts for protons in several proteins for which both detailed X-ray crystal structures and chemical shift assignments were available. For the classical point-dipole model, new proportionality constants were calculated by fitting to ring current estimations from both the quantum-mechanical Haigh-Mallion and semiclassical Johnson-Bovey methods and compared with the previously used point-dipole constant of Perkins and Dwek. Statistical analysis of the predictions obtained by all methods indicates that the point-dipole approximation parametrized against quantum-mechanical data is superior to the previously used classical model, comparable to Johnson-Bovey calculations, and slightly poorer than predictions from the Haigh-Mallion theory. The implementation of a pseudoenergy penalty term for use in structure refinement from chemical shift data based on the classical point-dipole model is described, and its usefulness in cases where other NMR information is limited is discussed with a specific example.
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Huang KX, Huang QL, Wildung MR, Croteau R, Scott AI. Overproduction, in Escherichia coli, of soluble taxadiene synthase, a key enzyme in the Taxol biosynthetic pathway. Protein Expr Purif 1998; 13:90-6. [PMID: 9631520 DOI: 10.1006/prep.1998.0870] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Taxadiene synthase catalyzes the conversion of the universal precursor of diterpenoids, geranylgeranyl diphosphate, to taxadiene, a key intermediate in Taxol (paclitaxel) biosynthesis. The gene encoding taxadiene synthase was cloned recently. Here we report a method for the heterologous overexpression of cDNA encoding taxadiene synthase in Escherichia coli using a thioredoxin fusion expression system, which increases the solubility of expressed protein. Taxadiene synthase cDNA was amplified by polymerase chain reaction and then subcloned into pET3d and pET32a(+) to form pET3dTX and pET32TX, respectively. The expressed taxadiene synthase from E. coli BL21(DE3)/pET3dTX was present completely as inclusion bodies. The transformant E. coli BL21(DE3)/pET32TX produced a thioredoxin fusion taxadiene synthase (15-20% of total soluble protein) when induced with isopropyl beta-D-thiogalactopyranoside at low temperature (20 degrees C). The recombinant enzyme was purified by a single step with a His-binding metal affinity column. The maximal production attained was 13 mg of purified, active fusion protein per 500 ml culture of E. coli BL21(DE3)/pET32TX. The purified recombinant taxadiene synthase fusion protein was similar to native protein in steady-state kinetic parameters and mobility on sodium sulfate-polyacrylamide gel electrophoresis. The protein purified from E. coli BL21(DE3)/pET3dTX had the expected N-terminal (AQLSFNA) sequence.
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Huang K, Huang QL, Scott AI. Overexpression, single-step purification, and site-directed mutagenetic analysis of casbene synthase. Arch Biochem Biophys 1998; 352:144-52. [PMID: 9521827 DOI: 10.1006/abbi.1998.0578] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Casbene synthase is a diterpene cyclase isolated from castor bean (Ricinus communis L), which catalyzes the cyclization of geranylgeranyl diphosphate to form the phytoalexin casbene. We here report the overexpression of casbene synthase in Escherichia coli in soluble form using a thioredoxin fusion system. The amplified DNA by PCR carried on pCS7 was inserted into the expression vector pET32b(+) to form pCAS.2. The resulting transformants of pCAS. 2/BL21(DE3) produced a thioredoxin casbene synthase fusion protein (20-30% of total soluble protein) when induced with isopropyl beta-d-thiogalactopyranoside at 20 degrees C. Recombinant casbene synthase was purified to homogeneity in a single step with a His-binding metal-affinity column. Casbene synthase has a conserved aspartate-rich region [amino acids 355-359 (DDTID)], one cysteine, and three histidines with several prenyl transferases and terpene cyclases. Seven mutants were constructed by site-directed mutagenesis. The importance of Asp 355 and Asp 356 for catalysis was established by an increase in Km as well as a reduction in kcat in the corresponding glutamate mutants. These results indicate that the first and the second aspartate are involved in catalysis, while the third aspartate and the conserved cysteine and histidine residues selected for mutagenesis appear not to be involved in catalysis.
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80
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Ahmed AA, Balboul BA, Scott AI, Williams HH, Miao B, Mabry TJ. Eudesmane derivatives from Iva frutescens. PHYTOCHEMISTRY 1998; 47:411-413. [PMID: 9433815 DOI: 10.1016/s0031-9422(97)00583-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Re-investigation of the aerial parts of Iva frutescens resulted in the isolation of three sesquiterpenes, two of which are new natural products, and their structures were established by spectral data.
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81
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Ian Scott A. How Nature Synthesizes B12 without Oxygen. Discoveries along the Ancient, Anaerobic Pathway. HETEROCYCLES 1998. [DOI: 10.3987/rev-97-sr(n)5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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82
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Williams HJ, Moyna G, Vinson SB, Scott AI, Bell AA, Stipanovic RD. β-Caryophyllene Derivatives from the Wild Cottons. ACTA ACUST UNITED AC 1997. [DOI: 10.1080/10575639708043753] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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83
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Moyna G, Williams HJ, Scott AI, Ringel I, Gorodetsky R, Swindell CS. Conformational studies of paclitaxel analogs modified at the C-2' position in hydrophobic and hydrophilic solvent systems. J Med Chem 1997; 40:3305-11. [PMID: 9379451 DOI: 10.1021/jm970026+] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The conformations of two paclitaxel analogs modified at the C-2' position, 2'-deoxypaclitaxel and 2'-methoxypaclitaxel, were studied in hydrophobic and hydrophilic solvent systems by a combination of NMR spectroscopy, CD measurements, and molecular modeling. Both analogs have hydrophobic and hydrophilic conformations that resemble those of paclitaxel itself in the same media. Since the two have diminished biological activities in a number of bioactivity assays and the hydrogen-bonding capability of the 2'-hydroxyl group has been eliminated, we postulate that this group is involved in hydrogen bonding with tubulin and plays an important role in molecular recognition. The results of this study are in agreement with our earlier report on paclitaxel 2'-acetate, an analog in which the 2'-hydroxyl group hydrogen-bonding capacity has also been eliminated.
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84
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Santander PJ, Roessner CA, Stolowich NJ, Holderman MT, Scott AI. How corrinoids are synthesized without oxygen: nature's first pathway to vitamin B12. CHEMISTRY & BIOLOGY 1997; 4:659-66. [PMID: 9331403 DOI: 10.1016/s1074-5521(97)90221-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
BACKGROUND During the biosynthesis of vitamin B12, the aerobic bacterium Pseudomonas denitrificans uses two enzymes, CobG and CobJ, to convert precorrin-3 to the ring-contracted intermediate, precorrin-4. CobG is a monooxygenase that adds a hydroxyl group, derived from molecular oxygen, to C-20, whereas CobJ is bifunctional, inserting a methyl group at C-17 of the macrocycle and catalyzing ring contraction. Molecular oxygen is not available to vitamin B12-producing anaerobic bacteria and members of the ancient Archaea, so the question arises of how these microbes accomplish the key ring-contraction process. RESULTS Cloning and overexpression of Salmonella typhimurium genes has led to the discovery that a single enzyme, CbiH, is responsible for ring contraction during anaerobic biosynthesis of vitamin B12. The process occurs when CbiH is incubated with precorrin-3, but only in the presence of cobalt. CbiH functions as a C-17 methyltransferase and mediates ring contraction and lactonization to yield the intermediate, cobalt-precorrin-4, isolated as cobalt-factor IV. 13C labeling studies have proved that cobalt-precorrin-4 is incorporated into cobyrinic acid, thereby confirming that cobalt-precorrin-4 is an intermediate in vitamin B12 biosynthesis. CONCLUSIONS Two distinct mechanisms exist in nature for the ring contraction of porphyrinoids to corrinoids-an ancient anaerobic pathway that requires cobalt complexation prior to nonoxidative rearrangement, and a more recent aerobic route in which molecular oxygen serves as the cofactor. The present results offer a rationale for the main differences between aerobic and anaerobic biosynthesis of vitamin B12. Thus, in anaerobes there is exchange of oxygen at the C-27 acetate site, extrusion of acetaldehyde and early insertion of cobalt, whereas the aerobes show no exchange of oxygen at C-27, extrude acetic acid and insert cobalt very late in the biosynthetic pathway, after ring contraction has occurred. These parallel routes to vitamin B12 have now been clearly distinguished by their differing mechanisms for ring contraction.
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85
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Moyna G, Hernandez G, Williams HJ, Nachman RJ, Scott AI. Development of Weiner et al. force field parameters suitable for conformational studies of [1,4]-benzodiazepines and related compounds. JOURNAL OF CHEMICAL INFORMATION AND COMPUTER SCIENCES 1997; 37:951-6. [PMID: 9316265 DOI: 10.1021/ci9700236] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A set of force field parameters capable of reproducing the preferred conformations of the biologically important [1,4]-benzodiazepines was developed for AMBER and other molecular modeling programs that utilize the Weiner et al. force field. Equilibrium parameters were obtained from representative model compounds found in the Cambridge Structural Database, and bond stretching and torsion potential force constants were estimated using AM1 and PM3 semiempirical Hamiltonians. Parameters obtained with the two semiempirical methods and the existing linear interpolation method are compared. Molecular mechanics and dynamic simulations showed that AM1 derived parameters, together with MNDO ESP fitted atomic charges, predicted the X-ray structure of a number of representative [1,4]-benzodiazepines within 0.01 A, 0.8 degree, and 5 degrees, from observed bond lengths, bond angles, and bond torsions, respectively.
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86
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Scott AI. Treatment of postnatal depression. Two weeks of depression may not be long enough to exclude spontaneous recovery. BMJ (CLINICAL RESEARCH ED.) 1997; 315:122. [PMID: 9240066 PMCID: PMC2127065 DOI: 10.1136/bmj.315.7100.122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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87
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Glen T, Scott AI. Recent registration and referrals from general practitioners. Br J Psychiatry 1997; 170:288-9. [PMID: 9229041 DOI: 10.1192/bjp.170.3.288b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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88
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Stolowich NJ, Frolov A, Atshaves B, Murphy EJ, Jolly CA, Billheimer JT, Scott AI, Schroeder F. The sterol carrier protein-2 fatty acid binding site: an NMR, circular dichroic, and fluorescence spectroscopic determination. Biochemistry 1997; 36:1719-29. [PMID: 9048555 DOI: 10.1021/bi962317a] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The interaction and orientation of fatty acids with recombinant human sterol carrier protein-2 (SCP-2) were examined by nuclear magnetic resonance (NMR), circular dichroism (CD), and fluorescence techniques. 13C-NMR spectroscopy of stearic acid and oleic acid as well as fluorescence spectroscopy of cis-parinaric acid demonstrated that SCP-2 bound naturally occurring fatty acids with near 1:1 stoichiometry. Several findings indicated that the fatty acid was oriented in the binding site with its methyl end buried in the protein interior and its carboxylate exposed at the surface: the chemical shift of bound [18-13C]-stearate; dicarboxylic/monocarboxylic acid cis-parinaric acid displacement; complete ionization of the carboxylate group of SCP-2 bound [1-13C]stearate at neutral pH; lack of electrostatic interactions between 13C-fatty acids with SCP-2 cationic residues: pH titratability of the SCP-2 bound [1-13C]stearate carboxylate group. SCP-2 did not undergo global structural changes upon ligand binding or pH decrease as indicated by the absence of significant changes in NMR and only small alterations in time resolved fluorescence parameters. However, SCP-2 did undergo secondary structural changes detected by CD in the pH range 5-6. While these changes in secondary structure did not alter the fatty acid:SCP-2 binding stoichiometry, the affinity for fatty acid was increased severalfold at lower pH. In summary, 13C-NMR, CD, and fluorescence spectroscopy provided a detailed understanding of the interaction of fatty acids with SCP-2 and further showed for the first time the orientation of the fatty acid within the binding site. The pH-induced changes in SCP-2 secondary structure and ligand binding activity may be important to the mechanism whereby this protein interacts with membrane surfaces to enhance lipid binding/transfer.
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Scott AI, Stolowich NJ, Wang J, Gawatz O, Fridrich E, Müller G. Biosynthesis of vitamin B12: factor IV, a new intermediate in the anaerobic pathway. Proc Natl Acad Sci U S A 1996; 93:14316-9. [PMID: 8962047 PMCID: PMC26128 DOI: 10.1073/pnas.93.25.14316] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/1996] [Accepted: 09/26/1996] [Indexed: 02/03/2023] Open
Abstract
The structure of a novel tetradehydrocorrin, factor IV, isolated from Propionibacterium shermanii has been established by multidimensional NMR spectroscopy. Incorporation of radiolabeled factor IV into cobyrinic acid established the biointermediacy of this cobalt complex, whose structure has implications for the mechanisms of the anaerobic pathway to B12.
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90
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Wang J, Stolowich NJ, Santander PJ, Park JH, Scott AI. Biosynthesis of vitamin B12: concerning the identity of the two-carbon fragment eliminated during anaerobic formation of cobyrinic acid. Proc Natl Acad Sci U S A 1996; 93:14320-2. [PMID: 8962048 PMCID: PMC26129 DOI: 10.1073/pnas.93.25.14320] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
It has been proved that, during anaerobic biosynthesis of the corrin macrocycle, the two-carbon fragment excised from the precursor, precorrin-3, is acetaldehyde, which originates from C-20 and its attached methyl group. This apparently contradictory finding is rationalized in terms of the subsequent enzymatic oxidation of acetaldehyde to acetic acid, which was previously regarded as the volatile fragment released by the action of the biosynthetic enzymes of Propionibacterium shermanii. The observation that acetaldehyde (rather than acetic acid) is extruded during anaerobic B12 synthesis is in full accord with the structure of factor IV, a new intermediate on the pathway.
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91
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Ahmed AA, Abd el-Razek MH, Abu Mostafa EA, Williams HJ, Scott AI, Reibenspies JH, Mabry TJ. A new derivative of glucose and 2-C-methyl-D-erythritol from Ferula sinaica. JOURNAL OF NATURAL PRODUCTS 1996; 59:1171-1173. [PMID: 8988602 DOI: 10.1021/np9603434] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A new glucose derivative (1) and 2-C-methyl-D-erythritol (2) were isolated from the leaves of Ferula sinaica. The two structures were elucidated by highfield NMR spectroscopy, and that of 1 was confirmed by X-ray diffraction analysis.
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92
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Park J, Tai J, Roessner CA, Scott AI. Enzymatic synthesis of S-adenosyl-L-methionine on the preparative scale. Bioorg Med Chem 1996; 4:2179-85. [PMID: 9022980 DOI: 10.1016/s0968-0896(96)00228-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The problems inherent in the enzymatic and chemical synthesis of S-adenosyl-L-methionine (SAM) led us to develop an efficient, simple method for the synthesis of large amounts of labeled SAM. Previously, we reported that the problem of product inhibition of E. coli SAM synthetase encoded by the metK gene was successfully overcome in the presence of sodium p-toluenesulfonate (pTsONa). This research has now been expanded to demonstrate that product inhibition of this enzyme can also be overcome by adding a high concentration of beta-mercaptoethanol (beta ME), acetonitrile, or urea. In addition a recombinant strain of E. coli has been constructed that expresses the yeast SAM synthetase encoded by the sam2 gene. The yeast enzyme does not have the problem of product inhibition seen with the E. coli enzyme. Complete conversion of 10 mM methionine to SAM was achieved in incubations with either the recombinant yeast enzyme and 1 molar potassium ion or the E. coli enzyme in the presence of additives such as beta ME, acetonitrile, urea, or pTsONa. The recombinant yeast SAM synthetase was used to generate SAM in situ for use in the multi-enzymatic synthesis of precorrin 2.
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93
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Moyna G, Mediwala S, Williams HJ, Scott AI. A simple algorithm for superimposing sets of NMR derived structures: its application to the conformational study of cephalomannine in lipophobic and lipophilic solution. JOURNAL OF CHEMICAL INFORMATION AND COMPUTER SCIENCES 1996; 36:1224-7. [PMID: 8941997 DOI: 10.1021/ci960118s] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A simple iterative method for superimposing sets of NMR derived structures and calculation of the root mean square deviation (RMSD) of the sets is described. It was compared to the commonly used algorithm involving pairwise best fitting in the conformational study of the taxoid anticancer drug cephalomannine in lipophobic and lipophilic solvents. Lower RMSD values were obtained, indicating a better superposition of the structures in the sets. The conformations of cephalomannine in the two solvent systems reported are in good agreement with earlier conformational studies on other active taxoids.
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94
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Roessner CA, Scott AI. Genetically engineered synthesis of natural products: from alkaloids to corrins. Annu Rev Microbiol 1996; 50:467-90. [PMID: 8905088 DOI: 10.1146/annurev.micro.50.1.467] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Because many natural products are of biological and medicinal importance, methods are continually being sought for studying their biosynthetic pathways, which may eventually result in increased production and the generation of novel compounds. Advances in genetic engineering have enabled the homologous or heterologous expression of many natural product biosynthetic genes from divergent sources, resulting in a supply of enzymes not readily available by isolation from the producing organism. Mixing and matching of these enzymes in cell-free reactions can provide information, not available by any other means, about enzyme mechanisms, pathway intermediates, and possible variations in the structure of the final product.
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95
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96
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Roessner CA, Scott AI. Achieving natural product synthesis and diversity via catalytic networking ex vivo. CHEMISTRY & BIOLOGY 1996; 3:325-30. [PMID: 8807860 DOI: 10.1016/s1074-5521(96)90114-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Recent studies on ex vivo synthesis of natural products reveal that even complex multistep pathways can be successfully reconstructed. Genetic engineering of such reconstituted pathways has already been used to generate 'unnatural' natural products related to the original compound. In the future, it may be possible to use these approaches to make natural products that are currently inaccessible to conventional synthesis.
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97
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Williams HJ, Moyna G, Scott AI, Swindell CS, Chirlian LE, Heerding JM, Williams DK. NMR and molecular modeling study of the conformations of taxol 2'-acetate in chloroform and aqueous dimethyl sulfoxide solutions. J Med Chem 1996; 39:1555-9. [PMID: 8691488 DOI: 10.1021/jm950796q] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Taxol 2'-acetate, an analog of the antitumor drug taxol, displays no significant in vitro microtubule polymerization activity, thus underscoring the importance of a free 2'-OH group to the biological activity of taxol. Previous work had suggested that the inactivity of taxol 2'-acetate is not due to steric interference by the acetyl group. The present study examined the conformations of taxol 2'-acetate in deuteriochloroform and (2)H2O-deuteriodimethyl sulfoxide solutions and found them to be essentially the same as the respective conformations adopted by taxol itself. Thus, neither destabilization of an active taxol conformation by the acetyl group nor the formation of an important taxol conformation determining role for the 2'-OH group appears likely. The implication of these findings is that the taxol 2'-OH group interacts directly with a protein residue in the taxol-microtubule complex, perhaps as a hydrogen bond donor.
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98
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Stolowich NJ, Wang J, Spencer JB, Santander PJ, Roessner CA, Scott AI. Absolute Stereochemistry of Precorrin-3x and Its Relevance to the Dichotomy of Ring Contraction Mechanism in Vitamin B12 Biosynthesis. J Am Chem Soc 1996. [DOI: 10.1021/ja952739s] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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99
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Ian Scott A, Shankar R. Chiral Lactams as Templates for Enzyme Inhibitors: A Simplified Route to the Expanded Pool. HETEROCYCLES 1996. [DOI: 10.3987/com-95-s56] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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100
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Williams HJ, Sattler I, Moyna G, Scott AI, Bell AA, Vinson SB. Diversity in cyclic sesquiterpene production by Gossypium hirsutum. PHYTOCHEMISTRY 1995; 40:1633-1636. [PMID: 8590634 DOI: 10.1016/0031-9422(95)00577-t] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Major sesquiterpene components of oil of Texas Race Stock 810 of Gossypium hirsutum were alpha- and beta-selinene. This is the seventh cyclic terpene type found to date in this genus. Both alpha- and beta-selinene, along with aromadendrene, were found but only as minor components of extracts of several domestic cultivars of G. hirsutum.
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