- The Interaction of Isopenicillin N Synthase with Homologated Substrate Analogues δ-(L-α-Aminoadipoyl)-L-homocysteinyl-D-Xaa Characterised by Protein Crystallography
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Isopenicillin N synthase (IPNS) converts the linear tripeptide δ-(L-α-aminoadipoyl)-L-cysteinyl-D-valine (ACV) into bicyclic isopenicillin N (IPN) in the central step in the biosynthesis of penicillin and cephalosporin antibiotics. Solution-phase incubation experiments have shown that IPNS turns over analogues with a diverse range of side chains in the third (valinyl) position of the substrate, but copes less well with changes in the second (cysteinyl) residue. IPNS thus converts the homologated tripeptides δ-(L-α-aminoadipoyl)-L-homocysteinyl-D-valine (AhCV) and δ-(L-α-aminoadipoyl)-L-homocysteinyl-D-allylglycine (AhCaG) into monocyclic hydroxy-lactam products; this suggests that the additional methylene unit in these substrates induces conformational changes that preclude second ring closure after initial lactam formation. To investigate this and solution-phase results with other tripeptides δ-(L-α-aminoadipoyl)-L-homocysteinyl-D-Xaa, we have crystallised AhCV and δ-(L-α-aminoadipoyl)-L-homocysteinyl-D-S-methylcysteine (AhCmC) with IPNS and solved crystal structures for the resulting complexes. The IPNS:FeII:AhCV complex shows diffuse electron density for several regions of the substrate, revealing considerable conformational freedom within the active site. The substrate is more clearly resolved in the IPNS:FeII:AhCmC complex, by virtue of thioether coordination to iron. AhCmC occupies two distinct conformations, both distorted relative to the natural substrate ACV, in order to accommodate the extra methylene group in the second residue. Attempts to turn these substrates over within crystalline IPNS using hyperbaric oxygenation give rise to product mixtures. Loose fit: IPNS catalyses the central step in penicillin biosynthesis. Substrate analogues containing L-homocysteine in place of the natural substrate's L-cysteine residue are not converted into bicyclic products. Crystal structures for IPNS complexes with two such analogues reveal that the additional CH2 unit affords considerable conformational freedom when these analogues bind to IPNS. Copyright
- Daruzzaman, Adam,Clifton, Ian J.,Adlington, Robert M.,Baldwin, Jack E.,Rutledge, Peter J.
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p. 599 - 606
(2013/06/04)
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- Controlling the position of functional groups at the liquid/solid interface: Impact of molecular symmetry and chirality
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With the aim of controlling the position of functional groups in a substrate-supported monolayer, a new family of functionalized linear alkyl chains was designed and synthesized, aided by molecular mechanics and dynamics simulations of its two-dimensional self-assembly on graphite. The self-assembly of these amino functionalized diamides at the liquid/solid interface was investigated with scanning tunneling microscopy. Intermolecular hydrogen-bonding interactions involving amides, combined with the effect of molecular symmetry and chirality, were found to guide the self-assembly. Control of the relative position and orientation of the amine groups was achieved, in the case of enantiopure compounds. Interestingly, racemates led to both racemic conglomerate and solid solution formation, with a concomitant loss of positional and orientational control of the amino groups as a result.
- De Cat, Inge,Gobbo, Cristian,Van Averbeke, Bernard,Lazzaroni, Roberto,De Feyter, Steven,Van Esch, Jan
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supporting information; experimental part
p. 20942 - 20950
(2012/02/13)
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- ALBUMIN-BINDING COMPOUNDS
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The present invention provides an albumin-binding compound essentially of the following elements: a spacer group, a water-soluble bridging group, a fatty acid chain and an acidic group characterised in that the acidic group is attached to the distal end of the fatty acid chain. The invention also provides an albumin-binding compound to which one or more biologically active moieties are attached.
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Page/Page column 22-23
(2010/02/15)
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- Crystallographic studies on the reaction of isopenicillin N synthase with an unsaturated substrate analogue
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Isopenicillin N synthase (IPNS) catalyses conversion of the linear tripeptie δ-(L-α-aminoadipoyl)-L-cysteinyl-D-valine (ACV) to isopenicillin N (IPN), the central step in biosynthesis of the β-lactam antibiotics. The unsaturated substrate analogue δ-(L-α-aminoadipoyl)-L-cysteinyl-D-vinylglycine (ACvG) has previously been incubated with IPNS and a single product was isolated, a 2-α-hydroxymethyl isopenicillin N (HMPen), formed via a monooxygenase mode of reactivity. ACvG has now been crystallised with IPNS and the structure of the anaerobic IPNS:Fe(II):ACvG complex determined to 1.15 A resolution. Furthermore, by exposing the anaerobically grown crystals to high-pressure oxygen gas, a structure corresponding to the bicyclic product HMPen has been obtained at 1.60 A resolution. In light of these and other IPNS structures, and recent developments with related dioxygenases, the [2 + 2] cycloaddition mechanism for HMPen formation from ACvG has been revised, and a stepwise radical mechanism is proposed. This revised mechanism remains consistent with the observed stereospecificity of the transformation, but fits better with apparent constraints on the coordination geometry around the active site iron atom.
- Elkins, Jonathan M.,Rutledge, Peter J.,Burzlaff, Nicolai I.,Clifton, Ian J.,Adlington, Robert M.,Roach, Peter L.,Baldwin, Jack E.
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p. 1455 - 1460
(2007/10/03)
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- PROPERTIES OF Nα,Nca-DI-TERT-BUTYLOXYCARBONYL-ω-CARBAMOYL-α-AMINO ACIDS AND DIRECT SYNTHESIS OF PROTECTED HOMOGLUTAMIC ACID DERIVATIVES
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The protected carboxamide function of Nα,Nca-di-tert-butyloxy-carbonyl-ω-carbamoyl-α-amino acids worked well with nucleophilic reagents.Applying this novel reactivity, we developed an efficient synthetic route to Nα-tert-butyloxycarbonylhomoglutamic acid and its derivatives, including Nα-tert-butyloxycarbonylhomoglutamic acid δ-benzyl ester, from Nα,Nca-di-tert-butyloxycarbonylhomoglutamine.KEYWORDS - protected homoglutamic acid synthesis; Nca-tert-butyloxycarbonylated carboxamide; hydrolysis; selective deprotection; Nα-tert-butyloxycarbonylhomoglutamic acid δ-benzyl ester; Nα-tert-butyloxycarbonylhomoglutamic acid α-tert-butyl ester; Nα-tert-butyloxycarbonylhomoglutamine; optical purity
- Sakura, Naoki,Hirose, Kyoko,Hashimoto, Tadashi
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p. 3506 - 3509
(2007/10/02)
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- Synthesis of Retrohydroxamate Analogues of the Microbial Iron-Transport Agent Ferrichrome
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A retrohydroxamate analogue (2) of the peptidyl iron transport agent ferrichrome 1 has been prepared in which transposition of the hydroxamate functionalities in the respective amino acid side chains, as compared to ferrichrome, has been effected.The requ
- Olsen, Richard K.,Ramasamy, K.
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p. 2264 - 2271
(2007/10/02)
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