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Affiliation(s)
- Xue‐Feng Zhu
- a Center for Biological Nuclear Magnetic Resonance (NMR), Department of Chemistry , Texas A&M University , College Station, Texas , USA
| | - A. Ian Scott
- a Center for Biological Nuclear Magnetic Resonance (NMR), Department of Chemistry , Texas A&M University , College Station, Texas , USA
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Abstract
Nucleoside mediated Claisen condensation of malonates has been achieved under biomimetic weak acid conditions, pH 3or 4, 0.15 M NaCl, and 0.125 M Mg(2+). The result illustrates the catalyzing property of end-nucleosides of t-RNA in the RNA world.
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Affiliation(s)
- Qi Ji
- Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, TX 77843, USA
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Abstract
The acquisition and sequencing of the genes encoding the enzymes for vitamin B12 biosynthesis in Salmonella typhimurium and Pseudomonas denitrificans has dramatically altered the direction of research on the pathway from uroporphyrinogen III to the corrinoids. Through a combination of molecular biology, organic chemistry and NMR spectroscopy, logical progression along the sequence is being made. Recent work from our laboratory is focused on the discovery and specificities of the methyltransferases connecting uroporphyrinogen III with cobyrinic acid, the temporal resolution of cobalt insertion and a comparison of the anaerobic pathway in S. typhimurium and the aerobic pathway in Ps. denitrificans. The implication of two parallel routes to corrins in these bacteria is discussed.
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Affiliation(s)
- A I Scott
- Department of Chemistry, Texas A&M University, College Station 77843-3255
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Kajiwara Y, Santander PJ, Roessner CA, Pérez LM, Scott AI. Genetically engineered synthesis and structural characterization of cobalt-precorrin 5A and -5B, two new intermediates on the anaerobic pathway to vitamin B12: definition of the roles of the CbiF and CbiG enzymes. J Am Chem Soc 2007; 128:9971-8. [PMID: 16866557 DOI: 10.1021/ja062940a] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Two new cobalt corrinoid intermediates, cobalt-precorrin 5A and cobalt-precorrin 5B, have been synthesized with the aid of overexpressed enzymes of the vitamin B(12) pathway of Salmonella entericaserovar typhimurium. These compounds were made in several regioselectively (13)C-labeled forms, and their structures have been established by multidimensional NMR spectroscopy. The addition of CbiF to the enzymes known to synthesize cobalt-precorrin 4 resulted in the formation of cobalt-precorrin 5A, and the inclusion of CbiG with CbiF produced cobalt-precorrin 5B, which has allowed us to define the role of these enzymes in the anaerobic biosynthetic pathway. CbiF is the C-11 methylase, and CbiG, an enzyme which shows homology with CobE of the aerobic pathway, is the gene product responsible for the opening of the ring A delta-lactone and extrusion of the "C(2)" unit. The discovery of these long-sought intermediates paves the way for defining the final stages of the anaerobic pathway. It is of considerable evolutionary interest that nature uses two distinct pathways to vitamin B(12), both conserved over several billion years and featuring completely different mechanisms for ring-contraction of the porphyrinoid to the corrinoid ring system. Thus the aerobic pathway utilizes molecular oxygen to trigger the events at C-20 leading to contraction and expulsion of the "C(2)" unit as acetic acid from a metal-free intermediate, whereas the anaerobic route features internal delivery of oxygen from a carboxylic acid terminus to C-20 followed by extrusion of the "C(2)" unit as acetaldehyde, using cobalt complexes as substrates.
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Affiliation(s)
- Yasuhiro Kajiwara
- Center for Biological NMR, Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, USA
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Kaczmarek K, Williams HJ, Coast GM, Scott AI, Zabrocki J, Nachman RJ. Comparison of insect kinin analogs withcis-peptide bond motif 4-aminopyroglutamate identifies optimal stereochemistry for diuretic activity. Biopolymers 2007; 88:1-7. [PMID: 17054115 DOI: 10.1002/bip.20613] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The insect kinins are present in a wide variety of insects and function as potent diuretic peptides, though they are subject to rapid degradation by internal peptidases. Insect kinin analogs incorporating stereochemical variants of (2S,4S)-4-aminopyroglutamate (APy), a cis-peptide bond motif, demonstrate significant activity in a cricket diuretic assay. Insect kinin analogs containing (2R,4R)-APy, (2S,4R)-APy and (2S,4S)-APy are essentially equipotent on an insect diuretic assay, with EC(50) values of about 10(-7)M, whereas the (2R,4S)-APy analog is at least 10-fold more potent (EC(50) = 7 x 10(-9)M). Conformational studies in aqueous solution indicate that the (2R,4S)-APy analog is considerably more flexible than the other three variants, which may explain its greater potency. The work identifies the optimal stereochemistry for the APy scaffold with which to design biostable, peptidomimetic analogs with the potential to disrupt critical insect kinin-regulated processes in insects.
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Affiliation(s)
- Krzysztof Kaczmarek
- Areawide Pest Management Research Unit, Southern Plains Agricultural Research Center, ARS, U.S. Department of Agriculture, College Station, TX 77845, USA
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Abstract
The genetic engineering of Escherichia coli for the over-expression of enzymes of the aerobic and anaerobic pathways to cobalamin has resulted in the in vivo and in vitro biosynthesis of new intermediates and other products that were isolated and characterized using a combination of bioorganic chemistry and high-resolution NMR. Analyses of these products were used to deduct the functions of the enzymes that catalyze their synthesis. CobZ, another enzyme for the synthesis of precorrin-3B of the aerobic pathway, has recently been described, as has been BluB, the enzyme responsible for the oxygen-dependent biosynthesis of dimethylbenzimidazole. In the anaerobic pathway, functions have recently been experimentally confirmed for or assigned to the CbiMNOQ cobalt transport complex, CbiA (a,c side chain amidation), CbiD (C-1 methylation), CbiF (C-11 methylation), CbiG (lactone opening, deacylation), CbiP (b,d,e,g side chain amidation), and CbiT (C-15 methylation, C-12 side chain decarboxylation). The dephosphorylation of adenosylcobalamin-phosphate, catalyzed by CobC, has been proposed as the final step in the biosynthesis of adenosylcobalamin.
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Affiliation(s)
- A. Ian Scott
- 1Center for Biological NMR, Department of Chemistry, Texas A and M University, College Station, TX 77843-3255, USA
| | - Charles A. Roessner
- 1Center for Biological NMR, Department of Chemistry, Texas A and M University, College Station, TX 77843-3255, USA
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Affiliation(s)
- Charles A Roessner
- Department of Chemistry, Center for Biological NMR, Texas A&M University, College Station, 77843-3255, USA.
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Pichon-Santander C, Santander PJ, Scott AI. Synthesis of substrate analogs of methyltransferases in the vitamin B12 biosynthetic pathway and characterization of their enzymatic products. Bioorg Med Chem 2006; 14:3904-22. [PMID: 16460949 DOI: 10.1016/j.bmc.2006.01.041] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2005] [Revised: 01/20/2006] [Accepted: 01/20/2006] [Indexed: 11/30/2022]
Abstract
The specificity toward substrate analogs of the first two methyltransferases in the vitamin B(12) biosynthetic pathway was probed with 15 synthetic porphyrinogens. Several novel methylated chlorins and isobacteriochlorins were isolated and characterized, suggesting the same methylation sequence C-2>C-7>C-20 as for the natural substrate, uro'gen III. The results allow us to narrow down possible structural requirements concerning substrate recognition by the methyltransferase enzymes.
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Abstract
The in vitro selection of RNAs catalyzing the decarboxylative Claisen condensation provides evidence for the synthesis of fatty acids, the building blocks of lipids and membranes, in the "RNA world".
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Affiliation(s)
- Youngha Ryu
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA
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Pichon-Santander C, Ian Scott A. Studies on the formation of porphyrinogens from monopyrroles in presence of the enzymes PBG deaminase and/or Uro’gen III synthase. Tetrahedron Lett 2005. [DOI: 10.1016/j.tetlet.2005.10.063] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Chow SY, Williams HJ, Huang Q, Nanda S, Scott AI. Studies on Taxadiene Synthase: Interception of the Cyclization Cascade at the Isocembrene Stage with GGPP Analogues. J Org Chem 2005; 70:9997-10003. [PMID: 16292833 DOI: 10.1021/jo0517489] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
[reaction: see text] The cyclization of GGPP to taxadiene, catalyzed by taxadiene synthase, has been suggested to proceed through a series of monocyclic isocembrenyl- and bicyclic verticillyl-carbocationic intermediary stages. A set of GGPP analogues with abolished or perturbed pi-nucleophilicity at the delta10 double bond (GGPP numbering) was synthesized and incubated with taxadiene synthase to intercept the cyclization cascade at the monocyclic stage. Each analogue was transformed by taxadiene synthase in vitro to hydrocarbon products in varying yields, and the structures of the major product in each reaction were solved by GCEIMS and one- and two-dimensional (1H and 13C) NMR and found to be 14-membered monocyclic isocembrenyl diterpenes, indicating that the first C-C bond formation catalyzed by taxadiene synthase could be uncoupled from the other subsequent bond formation events by using suitably designed substrate analogues. The formation and isolation of these isocembrenyl diterpene products using taxadiene synthase supports proposals that the isocembrenyl cation is an intermediate in the cyclization of GGPP to taxadiene.
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Affiliation(s)
- Siew Yin Chow
- Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, USA
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Santander PJ, Kajiwara Y, Williams HJ, Scott AI. Structural characterization of novel cobalt corrinoids synthesized by enzymes of the vitamin B12 anaerobic pathway. Bioorg Med Chem 2005; 14:724-31. [PMID: 16198574 DOI: 10.1016/j.bmc.2005.08.062] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2005] [Accepted: 08/26/2005] [Indexed: 11/23/2022]
Abstract
Investigation on the use of the oxidized form (factor 3 (3a)) of the trimethylated intermediate (precorrin 3 (2)) as a substrate for the enzymes of the anaerobic pathway to vitamin B12 led to the synthesis of three pairs of novel cobalt corrinoids. The products were made with the aid of the Salmonella typhimurium enzymes CbiH, CbiF, CbiG, and CbiT, were synthesized in several 13C labeled versions, and were isolated as methylesters after esterification. Structures were determined by detailed NMR and MS analyses. Each set of products was obtained in the decarboxylated (RMe) and non-decarboxylated (R=CH2COOCH3) forms (at the C-12 position of the porphyrinoid).
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Affiliation(s)
- Patricio J Santander
- Center for Biological NMR, Department of Chemistry, Texas A&M University, PO Box 3255, College Station, TX 77843-3255, USA.
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Roessner CA, Williams HJ, Scott AI. Genetically engineered production of 1-desmethylcobyrinic acid, 1-desmethylcobyrinic acid a,c-diamide, and cobyrinic acid a,c-diamide in Escherichia coli implies a role for CbiD in C-1 methylation in the anaerobic pathway to cobalamin. J Biol Chem 2005; 280:16748-53. [PMID: 15741157 DOI: 10.1074/jbc.m501805200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Co-expression of the cobA gene from Propionibacterium freudenreichii and the cbiA, -C, -D, -E, -T, -F, -G, -H, -J, -K, -L, and -P genes from Salmonella enterica serovar typhimurium in Escherichia coli resulted in the production of cobyrinic acid a,c-diamide. A cbiD deletion mutant of this strain produced 1-desmethylcobyrinic acid a,c-diamide, indicating that CbiD is involved in C-1 methylation in the anaerobic pathway to cobalamin. Strains that did not have the cbiP gene also produced 1-desmethylcobyrinic acid a,c-diamide, and strains that had neither cbiP nor cbiA synthesized 1-desmethylcobyrinic acid even in the presence of cbiD, suggesting that CbiA and CbiP are necessary for CbiD activity.
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Affiliation(s)
- Charles A Roessner
- Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, USA.
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McGoldrick HM, Roessner CA, Raux E, Lawrence AD, McLean KJ, Munro AW, Santabarbara S, Rigby SEJ, Heathcote P, Scott AI, Warren MJ. Identification and Characterization of a Novel Vitamin B12 (Cobalamin) Biosynthetic Enzyme (CobZ) from Rhodobacter capsulatus, Containing Flavin, Heme, and Fe-S Cofactors. J Biol Chem 2005; 280:1086-94. [PMID: 15525640 DOI: 10.1074/jbc.m411884200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
One of the most intriguing steps during cobalamin (vitamin B12) biosynthesis is the ring contraction process that leads to the extrusion of one of the integral macrocyclic carbon atoms from the tetrapyrrole-derived framework. The aerobic cobalamin pathway requires the action of a monooxygenase called CobG (precorrin-3B synthase), which generates a hydroxylactone intermediate that is subsequently ring-contracted by CobJ. However, in the photosynthetic bacterium Rhodobacter capsulatus, which harbors an aerobic-like pathway, there is no cobG in the main cobalamin biosynthetic operon although it does contain an additional uncharacterized gene called orf663. To demonstrate the involvement of Orf663 in cobalamin synthesis, the first dedicated 10 genes of the B12 pathway (including orf663), encoding enzymes for the transformation of uroporphyrinogen III into hydrogenobyrinic acid (HBA), were sequentially cloned into a plasmid to generate an artificial operon, which, when transformed into Escherichia coli, endowed the host with the ability to make HBA. Deletion of orf663 from this operon prevented HBA synthesis, demonstrating that it was essential for corrin construction. HBA synthesis was restored to this recombinant strain either by returning orf663 or by substituting it with cobG. Recombinant overproduction of Orf663, now renamed CobZ, allowed the characterization of a novel cofactor-rich protein, housing two Fe-S centers, a flavin, and a heme group, which like B12 itself is a modified tetrapyrrole. A mechanism for Orf663 (CobZ) in cobalamin biosynthesis is proposed.
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Affiliation(s)
- Helen M McGoldrick
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, United Kingdom
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Vévodová J, Graham RM, Raux E, Schubert HL, Roper DI, Brindley AA, Ian Scott A, Roessner CA, Stamford NPJ, Elizabeth Stroupe M, Getzoff ED, Warren MJ, Wilson KS. Structure/function studies on a S-adenosyl-L-methionine-dependent uroporphyrinogen III C methyltransferase (SUMT), a key regulatory enzyme of tetrapyrrole biosynthesis. J Mol Biol 2004; 344:419-33. [PMID: 15522295 DOI: 10.1016/j.jmb.2004.09.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Revised: 08/23/2004] [Accepted: 09/14/2004] [Indexed: 10/26/2022]
Abstract
The crystallographic structure of the Pseudomonas denitrificans S-adenosyl-L-methionine-dependent uroporphyrinogen III methyltransferase (SUMT), which is encoded by the cobA gene, has been solved by molecular replacement to 2.7A resolution. SUMT is a branchpoint enzyme that plays a key role in the biosynthesis of modified tetrapyrroles by controlling flux to compounds such as vitamin B(12) and sirohaem, and catalysing the transformation of uroporphyrinogen III into precorrin-2. The overall topology of the enzyme is similar to that of the SUMT module of sirohaem synthase (CysG) and the cobalt-precorrin-4 methyltransferase CbiF and, as with the latter structures, SUMT has the product S-adenosyl-L-homocysteine bound in the crystal. The roles of a number of residues within the SUMT structure are discussed with respect to their conservation either across the broader family of cobalamin biosynthetic methyltransferases or within the sub-group of SUMT members. The D47N, L49A, F106A, T130A, Y183A and M184A variants of SUMT were generated by mutagenesis of the cobA gene, and tested for SAM binding and enzymatic activity. Of these variants, only D47N and L49A bound the co-substrate S-adenosyl-L-methionine. Consequently, all the mutants were severely restricted in their capacity to synthesise precorrin-2, although both the D47N and L49A variants produced significant quantities of precorrin-1, the monomethylated derivative of uroporphyrinogen III. The activity of these variants is interpreted with respect to the structure of the enzyme.
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Affiliation(s)
- Jitka Vévodová
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5YW, UK
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Nanda S, Ian Scott A. A highly efficient chemoselective synthesis of 3,5-diketoesters by lipase-catalyzed transesterification: application to the resolution of secondary alcohols. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.molcatb.2004.02.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Abstract
[reaction: see text] Isoprenoid conjugates of nucleoside 5'-diphosphates were efficiently synthesized by one-step nucleophilic displacement reactions of either isoprenyl chlorides or isopentenyl tosylate with nucleoside 5'-diphosphates.
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Affiliation(s)
- Youngha Ryu
- Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, Texas 77843, USA
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Zhu XF, Williams HJ, Ian Scott A. Aqueous Trichloroacetic Acid: Another Useful Reagent for Highly Selective 5′-Desilylation of Multisilylated Nucleosides. SYNTHETIC COMMUN 2003. [DOI: 10.1081/scc-120021027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Abstract
The chronology of the discoveries along the pathway of vitamin B(12) biosynthesis is reviewed from a personal perspective, including discussion of the most recent finding that two pathways to B(12) exist-one aerobic and one anaerobic-which differ mainly in the ring contraction mechanisms that convert porphyrin to corrin.
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Affiliation(s)
- A Ian Scott
- Center for Biological NMR, Chemistry Department, Texas A&M University, 3255 TAMU, College Station, Texas 77843-3255, USA.
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Raux E, Leech HK, Beck R, Schubert HL, Santander PJ, Roessner CA, Scott AI, Martens JH, Jahn D, Thermes C, Rambach A, Warren MJ. Identification and functional analysis of enzymes required for precorrin-2 dehydrogenation and metal ion insertion in the biosynthesis of sirohaem and cobalamin in Bacillus megaterium. Biochem J 2003; 370:505-16. [PMID: 12408752 PMCID: PMC1223173 DOI: 10.1042/bj20021443] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2002] [Revised: 10/21/2002] [Accepted: 10/31/2002] [Indexed: 11/17/2022]
Abstract
In Bacillus megaterium, the hemAXBCDL genes were isolated and were found to be highly similar to the genes from Bacillus subtilis that are required for the conversion of glutamyl-tRNA into uroporphyrinogen III. Overproduction and purification of HemC (porphobilinogen deaminase) and -D (uroporphyrinogen III synthase) allowed these enzymes to be used for the in vitro synthesis of uroporphyrinogen III from porphobilinogen. A second smaller cluster of three genes (termed sirABC) was also isolated and found to encode the enzymes that catalyse the transformation of uroporphyrinogen III into sirohaem on the basis of their ability to complement a defined Escherichia coli (cysG) mutant. The functions of SirC and -B were investigated by direct enzyme assay, where SirC was found to act as a precorrin-2 dehydrogenase, generating sirohydrochlorin, and SirB was found to act as a ferrochelatase responsible for the final step in sirohaem synthesis. CbiX, a protein found encoded within the main B. megaterium cobalamin biosynthetic operon, shares a high degree of similarity with SirB and acts as the cobaltochelatase associated with cobalamin biosynthesis by inserting cobalt into sirohydrochlorin. CbiX contains an unusual histidine-rich region in the C-terminal portion of the protein, which was not found to be essential in the chelation process. Sequence alignments suggest that SirB and CbiX share a similar active site to the cobaltochelatase, CbiK, from Salmonella enterica.
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Affiliation(s)
- Evelyne Raux
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
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Roessner CA, Ponnamperuma K, Scott AI. Mutagenesis identifies a conserved tyrosine residue important for the activity of uroporphyrinogen III synthase from Anacystis nidulans. FEBS Lett 2002; 525:25-8. [PMID: 12163155 DOI: 10.1016/s0014-5793(02)03056-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Uroporphyrinogen III synthase from the cyanobacterium Anacystis nidulans was overproduced in Escherichia coli and analyzed by site specific mutagenesis. Of the nine conserved amino acids altered, only a single tyrosine mutant (Y166F) showed any significant decrease in activity suggesting this residue is critical for proper substrate binding and/or catalysis.
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Affiliation(s)
- Charles A Roessner
- Center for Biological NMR, Department of Chemsitry, P.O. Box 30012, Texas A&M University, College Station, TX 77842-3012, USA.
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Abstract
The biosynthesis of vitamin B(12) is summarized, emphasizing the differences observed between the aerobic and anaerobic pathways. The biosynthetic route to adenosylcobalamin from its five-carbon precursor, 5-aminolaevulinic acid, can be divided into three sections: (1) the biosynthesis of uroporphyrinogen III from 5-aminolaevulinic acid, which is common to both pathways; (2) the conversion of uroporphyrinogen III into the ring-contracted, deacylated intermediate precorrin 6 or cobalt-precorrin 6, which includes the primary differences between the two pathways; and (3) the transformation of this intermediate to form adenosylcobalamin.
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Affiliation(s)
- A I Scott
- Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA.
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Roessner CA, Huang KX, Warren MJ, Raux E, Scott AI. Isolation and characterization of 14 additional genes specifying the anaerobic biosynthesis of cobalamin (vitamin B12) in Propionibacterium freudenreichii (P. shermanii). Microbiology (Reading) 2002; 148:1845-1853. [PMID: 12055304 DOI: 10.1099/00221287-148-6-1845] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A search for genes encoding enzymes involved in cobalamin (vitamin B12) production in the commercially important organism Propionibacterium freudenreichii (P. shermanii) has resulted in the isolation of an additional 14 genes encoding enzymes responsible for 17 steps of the anaerobic B12 pathway in this organism. All of the genes believed to be necessary for the biosynthesis of adenosylcobinamide from uroporphyrinogen III have now been isolated except two (cbiA and an as yet unidentified gene encoding cobalt reductase). Most of the genes are contained in two divergent operons, one of which, in turn, is closely linked to the operon encoding the B12-dependent enzyme methylmalonyl-CoA mutase. The close linkage of the three genes encoding the subunits of transcarboxylase to the hemYHBXRL gene cluster is reported. The functions of the P. freudenreichii B12 pathway genes are discussed, and a mechanism for the regulation of cobalamin and propionic acid production by oxygen in this organism is proposed.
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Affiliation(s)
- Charles A Roessner
- Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA1
| | - Ke-Xue Huang
- Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA1
| | - Martin J Warren
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK2
| | - Evelyne Raux
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK2
| | - A Ian Scott
- Center for Biological NMR, Department of Chemistry, Texas A&M University, College Station, TX 77843-3255, USA1
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Scott AI, Kang J, Dalton D, Chung SK. Mechanism of action of coenzyme B12. An overall anionic mechanism for carbon-skeleton rearrangement in a model reaction. J Am Chem Soc 2002. [DOI: 10.1021/ja00479a055] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Evans JNS, Fagerness PE, Mackenzie NE, Scott AI. Biosynthesis of porphyrins and corrins. Direct observation of an enzyme-substrate complex by tritium NMR spectroscopy. J Am Chem Soc 2002. [DOI: 10.1021/ja00331a060] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chu PJ, Potrzebowski MJ, Scott AI, Gao Y. Conformational studies of N-benzoyl-L-phenylalanine by combined rotation and multiple-pulse spectroscopy proton nuclear magnetic resonance. J Am Chem Soc 2002. [DOI: 10.1021/ja00158a066] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Warren MJ, Gonzalez MD, Williams HJ, Stolowich NJ, Scott AI. Uroporphyrinogen III methylase catalyzes the enzymic synthesis of sirohydrochlorins II and IV by a clockwise mechanism. J Am Chem Soc 2002. [DOI: 10.1021/ja00169a048] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Spencer JB, Stolowich NJ, Roessner CA, Min C, Scott AI. Biosynthesis of vitamin B12: ring contraction is preceded by incorporation of molecular oxygen into precorrin-3. J Am Chem Soc 2002. [DOI: 10.1021/ja00077a075] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Malthouse JPG, Gamcsik MP, Boyd ASF, Mackenzie NE, Scott AI. Cryoenzymology of proteases: NMR detection of a productive thioacyl derivative of papain at subzero temperatures. J Am Chem Soc 2002. [DOI: 10.1021/ja00388a070] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Scott AI, Stolowich NJ, Atshaves BP, Karuso P, Warren MJ, Williams HJ, Kajiwara M, Kurumaya K, Okazaki T. Timing and mechanistic implications of regiospecific carbonyl oxygen isotope exchange during vitamin B12 biosynthesis. J Am Chem Soc 2002. [DOI: 10.1021/ja00026a047] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Gamcsik MP, Malthouse JPG, Primrose WU, Mackenzie NE, Boyd ASF, Russell RA, Scott AI. Structure and stereochemistry of tetrahedral inhibitor complexes of papain by direct NMR observation. J Am Chem Soc 2002. [DOI: 10.1021/ja00358a030] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Malthouse JPG, Mackenzie NE, Boyd ASF, Scott AI. Detection of a tetrahedral adduct in a trypsin-chloromethyl ketone specific inhibitor complex by carbon-13 NMR. J Am Chem Soc 2002. [DOI: 10.1021/ja00344a062] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ozaki S, Roessner CA, Stolowich NJ, Atshaves BP, Hertle R, Mueller G, Scott AI. Multienzyme synthesis and structure of factor S3. J Am Chem Soc 2002. [DOI: 10.1021/ja00071a001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Mueller G, Zipfel F, Hlineny K, Savvidis E, Hertle R, Traub-Eberhard U, Scott AI, Williams HJ, Stolowich NJ. Timing of cobalt insertion in vitamin B12 biosynthesis. J Am Chem Soc 2002. [DOI: 10.1021/ja00026a048] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Spencer JB, Stolowich NJ, Santander PJ, Pichon C, Kajiwara M, Tokiwa S, Takatori K, Scott AI. Mechanism of the Ring Contraction Step in Vitamin B12 Biosynthesis: The Origin and Subsequent Fate of the Oxygen Functionalities in Precorrin-3x. J Am Chem Soc 2002. [DOI: 10.1021/ja00090a056] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Scott AI, Williams HJ, Stolowich NJ, Karuso P, Gonzalez MD, Mueller G, Hlineny K, Savvidis E, Schneider E. Temporal resolution of the methylation sequence of vitamin B12 biosynthesis. J Am Chem Soc 2002. [DOI: 10.1021/ja00187a064] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Chung SK, Scott AI. Photosensitized oxygenation of trans,trans-1-methylcyclodeca-1,6-diene. Regiospecific hydroperoxidation with singlet oxygen. J Org Chem 2002. [DOI: 10.1021/jo00899a035] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Min C, Atshaves BP, Roessner CA, Stolowich NJ, Spencer JB, Scott AI. Isolation, structure, and genetically engineered synthesis of precorrin-5, the pentamethylated intermediate of vitamin B12 biosynthesis. J Am Chem Soc 2002. [DOI: 10.1021/ja00075a072] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Abstract
The chronology of the discoveries along the pathway of vitamin B12 biosynthesis is reviewed from a personal perspective, including discussion of the most recent finding that two pathways to B12 exist--one aerobic and one anaerobic--which differ mainly in the ring contraction mechanisms which convert porphyrin to corrin.
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Affiliation(s)
- A I Scott
- Center for Biological NMR, Chemistry Department, Texas A&M University, College Station 77843-3255, USA.
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Nachman RJ, Zabrocki J, Olczak J, Williams HJ, Moyna G, Ian Scott A, Coast GM. cis-peptide bond mimetic tetrazole analogs of the insect kinins identify the active conformation. Peptides 2002; 23:709-16. [PMID: 11897390 DOI: 10.1016/s0196-9781(01)00651-9] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The insect kinin neuropeptides have been implicated in the regulation of water balance, digestive organ contraction, and energy mobilization in a number of insect species. A previous solution conformation study of an active, restricted-conformation cyclic analog, identified two possible turn conformations as the likely active conformation adopted by the insect kinins at the receptor site. These were a cisPro type VI beta-turn over C-terminal pentapeptide core residues 1-4 and a transPro type I-like beta-turn over core residues 2-5, present in a ratio of 60:40. Synthesis and evaluation of the diuretic activity of insect kinin analogs incorporating a tetrazole moiety, which mimics a cis peptide bond, identifies the active conformation as the former. The discovery of a receptor interaction model can lead to the development of potent agonist and antagonist analogs of the insect kinins. Indeed, in this study a tetrazole analog with D stereochemistry has been shown to demonstrate partial antagonism of the diuretic activity of natural insect kinins, providing a lead for more potent and effective antagonists of this critical neuropeptide family. The future development of mimetic agonists and antagonists of insect kinin neuropeptides will provide important tools to neuroendocrinologists studying the mechanisms by which they operate and to researchers developing new, environmentally friendly pest insect control strategies.
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Affiliation(s)
- Ronald J Nachman
- Veterinary Entomology Research Laboratory, ARS, U.S. Department of Agriculture, 2881 F/B Road, College Station, TX 77845, USA.
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Yang D, Shipman LW, Roessner CA, Scott AI, Sacchettini JC. Structure of the Methanococcus jannaschii mevalonate kinase, a member of the GHMP kinase superfamily. J Biol Chem 2002; 277:9462-7. [PMID: 11751891 DOI: 10.1074/jbc.m110787200] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mevalonate-dependent pathway is used by many organisms to synthesize isopentenyl pyrophosphate, the building block for the biosynthesis of many biologically important compounds, including farnesyl pyrophosphate, dolichol, and many sterols. Mevalonate kinase (MVK) catalyzes a critical phosphoryl transfer step, producing mevalonate 5'-phosphate. The crystal structure of thermostable MVK from Methanococcus jannaschii has been determined at 2.4 A, revealing an overall fold similar to the homoserine kinase from M. jannaschii. In addition, the enzyme shows structural similarity with mevalonate 5-diphosphate decarboxylase and domain IV of elongation factor G. The active site of MVK is in the cleft between its N- and C-terminal domains. Several structural motifs conserved among species, including a phosphate-binding loop, have been found in this cavity. Asp(155), an invariant residue among MVK sequences, is located close to the putative phosphate-binding site and has been assumed to play the catalytic role. Analysis of the MVK model in the context of the other members of the GHMP kinase family offers the opportunity to understand both the mechanism of these enzymes and the structural details that may lead to the design of novel drugs.
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Affiliation(s)
- Dong Yang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2128 and Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255
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Abstract
The multiple actions of sterol carrier protein-2 (SCP-2) in intracellular lipid circulation and metabolism originate from its gene and protein structure. The SCP-x/pro-SCP-2 gene is a fusion gene with separate initiation sites coding for 15-kDa pro-SCP-2 (no enzyme activity) and 58-kDa SCP-x (a 3-ketoacyl CoA thiolase). Both proteins share identical cDNA and amino acid sequences for 13-kDa SCP-2 at their C-termini. Cellular 13-kDa SCP-2 derives from complete, posttranslational cleavage of the 15-kDa pro-SCP-2 and from partial posttranslational cleavage of 58-kDa SCP-x. Putative physiological functions of SCP-2 have been proposed on the basis of enhancement of intermembrane lipid transfer (e.g., cholesterol, phospholipid) and activation of enzymes involved in fatty acyl CoA transacylation (cholesterol esters, phosphatidic acid) in vitro, in transfected cells, and in genetically manipulated animals. At least four important SCP-2 structural domains have been identified and related to specific functions. First, the 46-kDa N-terminal presequence present in 58-kDa SCP-x is a 3-ketoacyl-CoA thiolase specific for branched-chain acyl CoAs. Second, the N-terminal 20 amino acid presequence in 15-kDa pro-SCP-2 dramatically modulates the secondary and tertiary structure of SCP-2 as well as potentiating its intracellular targeting coded by the C-terminal peroxisomal targeting sequence. Third, the N-terminal 32 amino acids form an amphipathic a-helical region, one face of which represents a membrane-binding domain. Positively charged amino acid residues in one face of the amphipathic helices allow SCP-2 to bind to membrane surfaces containing anionic phospholipids. Fourth, the hydrophobic faces of the N-terminal amphipathic a helices along with beta strands 4, 5, and helix D form a ligand-binding cavity able to accommodate multiple types of lipids (e. g., fatty acids, fatty acyl CoAs, cholesterol, phospholipids, isoprenoids). Two-dimensional 1H-15N heteronuclear single quantum coherence spectra of both apo-SCP-2 and of the 1:1 oleate-SCP-2 complex, obtained at pH 6.7, demonstrated the homogenous formation of holo-SCP-2. While comparison of the apo- and holoprotein amide fingerprints revealed about 60% of the resonances remaining essentially unchanged, 12 assigned amide residues underwent significant chemical-shift changes upon oleic acid binding. These residues were localized in three regions: the juncture of helices A and B, the mid-section of the beta sheet, and the interface formed by the region of beta strands 4, 5, and helix D. Circular dichroism also showed that these chemical-shift changes, upon oleic acid binding, did not alter the secondary structure of SCP-2. The nuclear magnetic resonance chemical shift difference data, along with mapping of the nearby hydrophobic residues, showed the oleic acid-binding site to be comprised of a pocket created by the face of the beta sheet, helices A and B on one end, and residues associated with beta strands 4, 5, and helix D at the other end of the binding cavity. Furthermore, the hydrophobic nature of the previously ill-defined C-terminus suggested that these 20 amino acids may form a 'hydrophobic cap' which closes around the oleic acid upon binding. Thus, understanding the structural domains of the SCP-x/pro-SCP-2 gene and its respective posttranslationally processed proteins has provided new insights into their functions in intracellular targeting and metabolism of lipids.
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Affiliation(s)
- N J Stolowich
- Department of Chemistry, University of Louisville, Kentucky 40292, USA
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