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Shoolingin-Jordan PM, Warren MJ, Awan SJ. Discovery that the assembly of the dipyrromethane cofactor of porphobilinogen deaminase holoenzyme proceeds initially by the reaction of preuroporphyrinogen with the apoenzyme. Biochem J 1996; 316 ( Pt 2):373-6. [PMID: 8687374 PMCID: PMC1217358 DOI: 10.1042/bj3160373] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The assembly process of the dipyrromethane cofactor of Escherichia coli porphobilinogen deaminase holoenzyme is initiated by the reaction of the porphobilinogen deaminase apoenzyme with preuroporphyrinogen. The resulting enzyme-bound tetrapyrrole (bilane) is equivalent to the holoenzyme intermediate complex ES2 and yields the dipyrromethane cofactor by reactions of the normal catalytic cycle. These observations indicate that preuroporphyrinogen, rather than porphobilinogen, is the preferred precursor for the dipyrromethane cofactor and explain the existence of the D84A and D84N deaminase mutants as catalytically inactive ES2 complexes.
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Louie GV, Brownlie PD, Lambert R, Cooper JB, Blundell TL, Wood SP, Malashkevich VN, Hädener A, Warren MJ, Shoolingin-Jordan PM. The three-dimensional structure of Escherichia coli porphobilinogen deaminase at 1.76-A resolution. Proteins 1996; 25:48-78. [PMID: 8727319 DOI: 10.1002/(sici)1097-0134(199605)25:1<48::aid-prot5>3.0.co;2-g] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Porphobilinogen deaminase (PBGD) catalyses the polymerization of four molecules of porphobilinogen to form the 1-hydroxymethylbilane, preuroporphyrinogen, a key intermediate in the biosynthesis of tetrapyrroles. The three-dimensional structure of wild-type PBGD from Escherichia coli has been determined by multiple isomorphous replacement and refined to a crystallographic R-factor of 0.188 at 1.76 A resolution. the polypeptide chain of PBGD is folded into three alpha/beta domains. Domains 1 and 2 have a similar overall topology, based on a five-stranded, mixed beta-sheet. These two domains, which are linked by two hinge segments but otherwise make few direct interactions, form an extensive active site cleft at their interface. Domain 3, an open-faced, anti-parallel sheet of three strands, interacts approximately equally with the other two domains. The dipyrromethane cofactor is covalently attached to a cysteine side-chain borne on a flexible loop of domain 3. The cofactor serves as a primer for the assembly of the tetrapyrrole product and is held within the active site cleft by hydrogen-bonds and salt-bridges that are formed between its acetate and propionate side-groups and the polypeptide chain. The structure of a variant of PBGD, in which the methionines have been replaced with selenomethionines, has also been determined. The cofactor, in the native and functional form of the enzyme, adopts a conformation in which the second pyrrole ring (C2) occupies an internal position in the active site cleft. On oxidation, however, this C2 ring of the cofactor adopts a more external position that may correspond approximately to the site of substrate binding and polypyrrole chain elongation. The side-chain of Asp84 hydrogen-bonds the hydrogen atoms of both cofactor pyrrole nitrogens and also potentially the hydrogen atom of the pyrrole nitrogen of the porphobilinogen molecule bound to the proposed substrate binding site. This group has a key catalytic role, possibly in stabilizing the positive charges that develop on the pyrrole nitrogens during the ring-coupling reactions. Possible mechanisms for the processive elongation of the polypyrrole chain involve: accommodation of the elongating chain within the active site cleft, coupled with shifts in the relative positions of domains 1 and 2 to carry the terminal ring into the appropriate position at the catalytic site; or sequential translocation of the elongating polypyrrole chain, attached to the cofactor on domain 3, through the active site cleft by the progressive movement of domain 3 with respect to domains 1 and 2. Other mechanisms are considered although the amino acid sequence comparisons between PBGDs from all species suggest they share the same three-dimensional structure and mechanism of activity.
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Furnell SM, Gaunt PN, Holben RF, Sanders PW, Stockel CT, Warren MJ. Assessing staff attitudes towards information security in a European healthcare establishment. MEDICAL INFORMATICS = MEDECINE ET INFORMATIQUE 1996; 21:105-12. [PMID: 8947888 DOI: 10.3109/14639239608995012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Information security is now recognized as an important consideration in modern healthcare establishments (HCEs), with a variety of guidelines and standards currently available to enable the environments to be properly protected. However, financial and operational constraints often exist which influence the practicality of these recommendations. This paper establishes that the staff culture of the organization is of particular importance in determining the level and types of security that will be accepted. This culture will be based upon staff awareness of and attitudes towards security and it is, therefore, important to have a clear idea of what these attitudes are. To this end, two surveys have been conducted within a reference environment to establish the attitudes of general users and technical staff, allowing the results to be fed back to HCE management to enable security policy to be appropriately defined. These results indicated that, although the establishment had participated in a European healthcare security initiative, staff attitudes and awareness were still weak in some areas.
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Raux E, Lanois A, Levillayer F, Warren MJ, Brody E, Rambach A, Thermes C. Salmonella typhimurium cobalamin (vitamin B12) biosynthetic genes: functional studies in S. typhimurium and Escherichia coli. J Bacteriol 1996; 178:753-67. [PMID: 8550510 PMCID: PMC177722 DOI: 10.1128/jb.178.3.753-767.1996] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
In order to study the Salmonella typhimurium cobalamin biosynthetic pathway, the S. typhimurium cob operon was isolated and cloned into Escherichia coli. This approach has given the new host of the cob operon the ability to make cobalamins de novo, an ability that had probably been lost by this organism. In total, 20 genes of the S. typhimurium cob operon have been transferred into E. coli, and the resulting recombinant strains have been shown to produce up to 100 times more corrin than the parent S. typhimurium strain. These measurements have been performed with a quantitative cobalamin microbiological assay which is detailed in this work. As with S. typhimurium, cobalamin synthesis is only observed in the E. coli cobalamin-producing strains when they are grown under anaerobic conditions. Derivatives of the cobalamin-producing E. coli strains were constructed in which genes of the cob operon were inactivated. These strains, together with S. typhimurium cob mutants, have permitted the determination of the genes necessary for cobalamin production and classification of cbiD and cbiG as cobl genes. When grown in the absence of endogenous cobalt, the oxidized forms of precorrin-2 and precorrin-3, factor II and factor III, respectively, were found to accumulate in the cytosol of the corrin-producing E. coli. Together with the finding that S. typhimurium cbiL mutants are not complemented with the homologous Pseudomonas denitrificans gene, these results lend further credence to the theory that cobalt is required at an early stage in the biosynthesis of cobalamins in S. typhimurium.
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Woodcock SC, Warren MJ. Evidence for a covalent intermediate in the S-adenosyl-L-methionine-dependent transmethylation reaction catalysed by sirohaem synthase. Biochem J 1996; 313 ( Pt 2):415-21. [PMID: 8573073 PMCID: PMC1216924 DOI: 10.1042/bj3130415] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
CysG, also known as uroporphyrinogen III methylase and sirohaem synthase (CysG; EC 2.1.1.107), is a multifunctional enzyme that is able to transform uroporphyrinogen III into sirohaem via two S-adenosyl-L-methionine (AdoMet)-dependent transmethylations, an NAD(+)-dependent dehydrogenation and a ferrochelation. The apparent tight binding of AdoMet to this multifunctional enzyme is investigated. The use of a rapid AdoMet binding assay demonstrates that CysG becomes labelled with both [methyl-3H]AdoMet and [carboxyl-14C]AdoMet. Further experiments show that the CysG-AdoMet complex is subsequently able to methylate uroporphyrinogen III. CysG remains associated with the labelled constituents of the AdoMet even after denaturation with urea and SDS/PAGE, suggesting that the AdoMet has become covalently linked to the protein. A rapid examination of some of the other transmethylases involved in corrin biosynthesis reveals that they bind the AdoMet in a similar fashion. A multistep transmethylation mechanism is proposed to explain the observed results.
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Warren MJ, Gul S, Aplin RT, Scott AI, Roessner CA, O'Grady P, Shoolingin-Jordan PM. Evidence for conformational changes in Escherichia coli porphobilinogen deaminase during stepwise pyrrole chain elongation monitored by increased reactivity of cysteine-134 to alkylation by N-ethylmaleimide. Biochemistry 1995; 34:11288-95. [PMID: 7669787 DOI: 10.1021/bi00035a038] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Porphobilinogen deaminase from Escherichia coli becomes progressively more susceptible to inactivation by the thiophilic reagent N-ethylmaleimide (NEM) as the catalytic cycle proceeds through the enzyme-intermediate complexes ES, ES2, ES3, and ES4. Site-directed mutagenesis of potentially reactive cysteines has been used to identify cysteine-134 as the key residue that becomes modified by the reagent and leads to inactivation. Since cysteine-134 is buried at the interface between domains 2 and 3 of the E. coli deaminase molecule, the observations suggest that a stepwise conformational change occurs between these domains during each stage of tetrapyrrole assembly. Interestingly, mutation of the invariant active-site cysteine-242 to serine leads to an enzyme with up to a third of the catalytic activity found in the wild-type enzyme. Electrospray mass spectrometry indicates that serine can substitute for cysteine as the dipyrromethane cofactor attachment site.
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Furnell SM, Sanders PW, Warren MJ. Development of security guidelines for existing healthcare systems. MEDICAL INFORMATICS = MEDECINE ET INFORMATIQUE 1995; 20:139-48. [PMID: 8569307 DOI: 10.3109/14639239509025352] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
As modern healthcare establishments become increasingly dependent upon information systems it is vital to ensure that adequate security is present to safeguard the confidentiality and integrity of data and the availability of systems. Whilst this is now generally recognized in the design of new systems, many existing operational systems have been implemented without security in mind. This paper describes the need for a standardized approach in the protection of existing healthcare systems within Europe and presents an overview of a new set of information security guidelines that have been developed specifically for the medical community. The guidelines discussed have been produced as a deliverable of the Commission of European Communities (CEC) SEISMED (Secure Environment for Information Systems in Medicine) project, under the Advanced Informatics in Medicine (AIM) programme.
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Wilkie SE, Roper JM, Smith AG, Warren MJ. Isolation, characterisation and expression of a cDNA clone encoding plastid aspartate aminotransferase from Arabidopsis thaliana. PLANT MOLECULAR BIOLOGY 1995; 27:1227-33. [PMID: 7766905 DOI: 10.1007/bf00020897] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
A clone encoding aspartate aminotransferase (AAT, EC 2.6.1.1) was isolated from an Arabidopsis thaliana leaf cDNA library. This clone contains a 1365 bp open reading frame encoding a polypeptide of 49.8 kDa, designated Ataat1. The clone was shown to contain a chloroplastic isoenzyme as an in organellar protein import assay demonstrated that a radiolabelled transcription/translation product of 49.8 kDa was imported into viable pea chloroplasts and was subsequently processed to yield a mature protein of 45 kDa. The open reading frame corresponding to the predicted mature AAT was manipulated into an expression construct (pEC14). Transformed Escherichia coli cells containing pEC14 expressed up to 16 times more AAT activity than vector only controls, thus demonstrating conclusively that the clone encoded AAT.
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159
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Brownlie PD, Lambert R, Louie GV, Jordan PM, Blundell TL, Warren MJ, Cooper JB, Wood SP. The three-dimensional structures of mutants of porphobilinogen deaminase: toward an understanding of the structural basis of acute intermittent porphyria. Protein Sci 1994; 3:1644-50. [PMID: 7849582 PMCID: PMC2142616 DOI: 10.1002/pro.5560031004] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Mutations in the human gene for the enzyme porphobilinogen deaminase give rise to an inherited disease of heme biosynthesis, acute intermittent porphyria. Knowledge of the 3-dimensional structure of human porphobilinogen deaminase, based on the structure of the bacterial enzyme, allows correlation of structure with gene organization and leads to an understanding of the relationship between mutations in the gene, structural and functional changes of the enzyme, and the symptoms of the disease. Most mutations occur in exons 10 and 12, often changing amino acids in the active site. Several of these are shown to be involved in binding the primer or substrate; none modifies Asp 84, which is essential for catalytic activity.
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160
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Warren MJ, Bolt EL, Roessner CA, Scott AI, Spencer JB, Woodcock SC. Gene dissection demonstrates that the Escherichia coli cysG gene encodes a multifunctional protein. Biochem J 1994; 302 ( Pt 3):837-44. [PMID: 7945210 PMCID: PMC1137306 DOI: 10.1042/bj3020837] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The C-terminus of the Escherichia coli CysG protein, consisting of amino acids 202-457, was expressed as a recombinant protein using gene dissection methodology. Analysis of the activity of this truncated protein, termed CysGA, revealed that it was able to methylate uroporphyrinogen III in the same S-adenosyl-L-methionine (SAM)-dependent manner as the complete CysG protein. However, this truncated protein was not able to complement E. coli cysG cells, thereby suggesting that the first 201 amino acids of the CysG protein had an enzymic activity associated with the conversion of dihydrosirohydrochlorin into sirohaem. Analysis of the N-terminus of the CysG protein revealed the presence of a putative pyridine dinucleotide binding site. When the purified CysG protein was incubated with NADP+, uroporphyrinogen III and SAM the enzyme was found to catalyse a coenzyme-mediated dehydrogenation to form sirohydrochlorin. The CysGA protein on the other hand showed no such coenzyme-dependent activity. Analysis of the porphyrinoid material isolated from strains harbouring plasmids containing the complete and truncated cysG genes suggested that the CysG protein was also involved in ferrochelation. The evidence presented in this paper suggests that the CysG protein is a multifunctional protein involved in SAM-dependent methylation, pyridine dinucleotide dependent dehydrogenation and ferrochelation.
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Furnell SM, Gaunt PN, Pangalos G, Sanders PW, Warren MJ. A generic methodology for health care data security. MEDICAL INFORMATICS = MEDECINE ET INFORMATIQUE 1994; 19:229-45. [PMID: 7707744 DOI: 10.3109/14639239409025329] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The aim is to outline the framework of a generic methodology for specifying countermeasures in health care environments. The method is specifically aimed at the enhancement of security in existing health care systems, and a key element is the use of predetermined 'profiles' by which these may be classified. Example scenarios are presented to illustrate how the concept could be applied in practice. The paper is based upon work that was initially carried out as part of the Commission of European Communities SEISMED (Secure Environment for Information Systems in MEDicine) project, the aim of which is to provide security recommendations for European health care establishments (HCEs).
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Louie GV, Brownlie PD, Lambert R, Cooper JB, Blundell TL, Wood SP, Warren MJ, Woodcock SC, Jordan PM. Structure of porphobilinogen deaminase reveals a flexible multidomain polymerase with a single catalytic site. Nature 1992; 359:33-9. [PMID: 1522882 DOI: 10.1038/359033a0] [Citation(s) in RCA: 133] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The three-domain structure of porphobilinogen deaminase, a key enzyme in the biosynthetic pathway of tetrapyrroles, has been defined by X-ray analysis at 1.9 A resolution. Two of the domains structurally resemble the transferrins and periplasmic binding proteins. The dipyrromethane cofactor is covalently linked to domain 3 but is bound by extensive salt-bridges and hydrogen-bonds within the cleft between domains 1 and 2, at a position corresponding to the binding sites for small-molecule ligands in the analogous proteins. The X-ray structure and results from site-directed mutagenesis provide evidence for a single catalytic site. Interdomain flexibility may aid elongation of the polypyrrole product in the active-site cleft of the enzyme.
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Roessner CA, Warren MJ, Santander PJ, Atshaves BP, Ozaki S, Stolowich NJ, Iida K, Scott AI. Expression of 9 Salmonella typhimurium enzymes for cobinamide synthesis. Identification of the 11-methyl and 20-methyl transferases of corrin biosynthesis. FEBS Lett 1992; 301:73-8. [PMID: 1451790 DOI: 10.1016/0014-5793(92)80213-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nine of the cbi genes from the 17.5 kb cob operon of Salmonella typhimurium previously shown by genetic studies to be involved in the biosynthesis of cobinamide from precorrin-2, have been subcloned and expressed in Escherichia coli. Seven of the gene products were found in the soluble fraction of cell lysates and have been purified. The gene products corresponding to cbi E, F, H and L were shown by SAM binding and by homology with other SAM-binding proteins to be candidates for the methyltransferases of vitamin B12 biosynthesis. The enzymatic functions of the gene products of cbiL and cbiF are associated with C-methylation at C-20 of precorrin-2 and C-11 of precorrin-3.
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Jordan PM, Warren MJ, Mgbeje BI, Wood SP, Cooper JB, Louie G, Brownlie P, Lambert R, Blundell TL. Crystallization and preliminary X-ray investigation of Escherichia coli porphobilinogen deaminase. J Mol Biol 1992; 224:269-71. [PMID: 1548705 DOI: 10.1016/0022-2836(92)90590-g] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Porphobilinogen deaminase, the polymerase that catalyses the synthesis of preuroporphyrinogen, the linear tetrapyrrole precursor of uroporphyrinogen III, has been crystallized from sodium acetate buffer with polyethylene glycol 6000 as precipitant. The crystals are orthorhombic and the space group is P2(1)2(1)2, with unit cell dimensions a = 88.01 A, b = 75.86 A, c = 50.53 A and alpha = beta = gamma = 90 degrees, indicating a single molecule of 34 kDa in the asymmetric unit. The crystals grow to dimensions of 1 mm x 2 mm x 0.5 mm within two weeks in the dark and are stable in the X-ray beam for at least 40 hours. Diffraction data beyond 1.7 A resolution, observed with a synchrotron radiation source, indicate that a high resolution structure analysis is feasible.
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Warren MJ, Roessner CA, Ozaki S, Stolowich NJ, Santander PJ, Scott AI. Enzymatic synthesis and structure of precorrin-3, a trimethyldipyrrocorphin intermediate in vitamin B12 biosynthesis. Biochemistry 1992; 31:603-9. [PMID: 1731915 DOI: 10.1021/bi00117a043] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The trimethylated intermediate of vitamin B12 (corrin) biosynthesis, precorrin-3, was produced from various 13C-enriched isotopomers of 5-aminolevulinic acid (ALA), using a multiple-enzyme system containing ALA dehydratase, porphobilinogen deaminase, uro'gen III synthetase, and the S-adenosyl-L-methionine-(SAM)-dependent uro'gen III methyltransferase (M-1) and precorrin-2 methyltransferase (M-2) in the presence of [13C]SAM. Structural analysis of the resulting product, precorrin-3, reveals a close similarity to precorrin-2 but with several subtle differences in the conjugated array of C = C and C = N bonds which reflect the presence of the new C-methyl group at C20 and its influence on the electronic distribution in the dipyrrocorphin chromophore. The implications of this structure for corrin biosynthesis are discussed.
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Aplin RT, Baldwin JE, Pichon C, Roessner CA, Ian Scott A, Schofield CJ, Stolowich NJ, Warren MJ. Observation of enzyme bound intermediates in the biosynthesis of preuroporphyrinogen by PBG deaminase. Bioorg Med Chem Lett 1991. [DOI: 10.1016/s0960-894x(01)80453-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Warren MJ. Radiography of the paranasal sinuses--one or three views? Clin Radiol 1991; 43:69. [PMID: 2053938 DOI: 10.1016/s0009-9260(05)80363-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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171
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Warren MJ, Scott AI. Tetrapyrrole assembly and modification into the ligands of biologically functional cofactors. Trends Biochem Sci 1990; 15:486-91. [PMID: 2077690 DOI: 10.1016/0968-0004(90)90304-t] [Citation(s) in RCA: 98] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Data obtained using a combination of molecular biology and NMR spectroscopy has transformed our thinking about the evolution of the biochemical machinery required for the synthesis of the vital metallopigments: haem, chlorophyll, vitamin B12 and factor F430. One of the most recent advances is the discovery of a unique dipyrromethane cofactor that is bound covalently at the active site of porphobillinogen deaminase, the key enzyme of tetrapyrrole assembly. We will also discuss how the oxidation level and chromophoric arrangement of the uroporphinoid ring, rather than its substitution pattern, provides the necessary molecular recognition for some of the later enzymes, whose function is to decorate the template by C-methylation on the way to the biologically active cofactors.
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Warren MJ, Jeffree MA, Wilson DJ, MacLarnon JC. Computed tomography in suspected tarsal coalition. Examination of 26 cases. ACTA ORTHOPAEDICA SCANDINAVICA 1990; 61:554-7. [PMID: 2281765 DOI: 10.3109/17453679008993582] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Coronal plane computed tomography (CT) was performed in 26 consecutive patients with clinical suspicion of tarsal coalition. Twenty patients had plain CT and 6 had CT talocalcaneonavicular arthrography. Fifteen patients were found to have coalition. Of these 15 patients, 12 had talocalcaneal coalition (9 bilateral, 3 unilateral), 2 patients had combined talocalcaneal and calcaneonavicular coalitions, and the remaining patient had bilateral calcaneonavicular coalitions. Surgical findings corroborated the CT diagnosis in 9 patients with talocalcaneal coalition and in 2 patients with calcaneonavicular coalition. Ossified talocalcaneal coalitions were found in children aged 6 and 10 years, i.e., well below the conventionally stated age range of 12 to 16 years. CT is the investigation of choice in suspected tarsal coalition if plain radiography is not diagnostic. CT arthrography did not generally provide further information, but may be useful if plain CT is equivocal.
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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 [Erratum to document cited in CA113(3):20050w]. J Am Chem Soc 1990. [DOI: 10.1021/ja00177a078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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174
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Warren MJ, Stolowich NJ, Santander PJ, Roessner CA, Sowa BA, Scott AI. Enzymatic synthesis of dihydrosirohydrochlorin (precorrin-2) and of a novel pyrrocorphin by uroporphyrinogen III methylase. FEBS Lett 1990; 261:76-80. [PMID: 2407558 DOI: 10.1016/0014-5793(90)80640-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Uroporphyrinogen III methylase was purified from a recombinant hemB-strain of E. coli harbouring a plasmid containing the cysG gene. N-terminal analysis of this purified protein gave an amino acid sequence corresponding to that predicted from the genetic code. From the u.v./visible spectrum of the reaction catalysed by this SAM dependent methylase it was possible to observe the sequential appearance of the chromophores of a dipyrrocorphin and subsequently of a pyrrocorphin. Confirmation of this transformation was obtained from 13C-NMR studies when it was demonstrated, for the first time directly, that uroporphyrinogen is initially converted into dihydrosirohydrochlorin (precorrin-2) and then, by further methylation, into a novel trimethylpyrrocorphin.
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Scott AI, Warren MJ, Roessner CA, Stolowich NJ, Santander PJ. Development of an ‘overmethylation’ strategy for corrin synthesis. Multi-enzyme preparation of pyrrocorphins. ACTA ACUST UNITED AC 1990. [DOI: 10.1039/c39900000593] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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