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Ian A Wilson

Publications and source records attributed to Ian A Wilson.

At least 37 records · Page 2Linked to original sources
PubMed2006

Discovery of a potent, nonpolyglutamatable inhibitor of glycinamide ribonucleotide transformylase.

Glycinamide ribonucleotide transformylase (GAR Tfase) catalyzes the first of two formyl transfer steps in the de novo purine biosynthetic pathway that require folate cofactors. Herein we report the discovery of a potent, nonpolyglutamatable, and selective inhibitor of GAR Tfase. Compound 12, which possesses a tetrazole in place of the gamma-carboxylic acid in the l-glutamate subunit of the potent GAR Tfase inhibitor 1, was active in cellular-based functional assays exhibiting purine-sensitive cytotoxic activity (IC(50) = 40 nM, CCRF-CEM) and was selective for inhibition of rhGAR Tfase (K(i) = 130 nM). Notably, 12 was only 2.5-fold less potent than 1 in cellular assays and 4-fold less potent against rhGAR Tfase. Like 1, this functional activity of 12 in the cell-based assay benefits from and requires transport into the cell by the reduced folate carrier but, unlike 1, is independent of folyl polyglutamate synthase (FPGS) expression levels and polyglutamation.

Aminobutyrates↗
PubMed2006

Solution structure of Asl1650, an acyl carrier protein from Anabaena sp. PCC 7120 with a variant phosphopantetheinylation-site sequence.

Cyanobacteria, such as Anabaena, produce a variety of bioactive natural products via polyketide synthases (PKS), nonribosomal peptide synthetases (NRPS), and hybrid peptide/polyketide pathways. The protein Asl1650, which is a member of the acyl carrier protein family from the cyanobacterium Anabaena sp. PCC 7120, is encoded in a region of the Anabaena genome that is rich in PKS and NRPS genes. To gain new insight into the physiological role of acyl carriers in Anabaena, the solution structure of Asl1650 has been solved by NMR spectroscopy. The protein adopts a twisted antiparallel four-helix bundle fold, with a variant phosphopantetheine-attachment motif positioned at the start of the second helix. Structure comparisons with proteins from other organisms suggest a likely physiological function as a discrete peptidyl carrier protein.

Acyl Carrier Protein↗
PubMed2006

Structure and receptor specificity of the hemagglutinin from an H5N1 influenza virus.

The hemagglutinin (HA) structure at 2.9 angstrom resolution, from a highly pathogenic Vietnamese H5N1 influenza virus, is more related to the 1918 and other human H1 HAs than to a 1997 duck H5 HA. Glycan microarray analysis of this Viet04 HA reveals an avian alpha2-3 sialic acid receptor binding preference. Introduction of mutations that can convert H1 serotype HAs to human alpha2-6 receptor specificity only enhanced or reduced affinity for avian-type receptors. However, mutations that can convert avian H2 and H3 HAs to human receptor specificity, when inserted onto the Viet04 H5 HA framework, permitted binding to a natural human alpha2-6 glycan, which suggests a path for this H5N1 virus to gain a foothold in the human population.

Amino Acid Sequence↗
PubMed2006

Design of natural killer T cell activators: structure and function of a microbial glycosphingolipid bound to mouse CD1d.

Natural killer T (NKT) cells provide an innate-type immune response upon T cell receptor interaction with CD1d-presented antigens. We demonstrate through equilibrium tetramer binding and antigen presentation assays with Valpha14i-positive NKT cell hybridomas that the Sphingomonas glycolipid alpha-galacturonosyl ceramide (GalA-GSL) is a NKT cell agonist that is significantly weaker than alpha-galactosylceramide (alpha-GalCer), the most potent known NKT agonist. For GalA-GSL, a shorter fatty acyl chain, an absence of the 4-OH on the sphingosine tail and a 6'-COOH group on the galactose moiety account for its observed antigenic potency. We further determined the crystal structure of mCD1d in complex with GalA-GSL at 1.8-A resolution. The overall binding mode of GalA-GSL to mCD1d is similar to that of the short-chain alpha-GalCer ligand PBS-25, but its sphinganine chain is more deeply inserted into the F' pocket due to alternate hydrogen-bonding interactions between the sphinganine 3-OH with Asp-80. Subsequently, a slight lateral shift (>1 A) of the galacturonosyl head group is noted at the CD1 surface compared with the galactose of alpha-GalCer. Because the relatively short C(14) fatty acid of GalA-GSL does not fully occupy the A' pocket, a spacer lipid is found that stabilizes this pocket. The lipid spacer was identified by GC/MS as a mixture of saturated and monounsaturated palmitic acid (C(16)). Comparison of available crystal structures of alpha-anomeric glycosphingolipids now sheds light on the structural basis of their differential antigenic potency and has led to the design and synthesis of NKT cell agonists with enhanced cell-based stimulatory activities compared with alpha-GalCer.

Animals↗
PubMed2006

Cofactor-containing antibodies: crystal structure of the original yellow antibody.

Antibodies are generally thought to be a class of proteins that function without the use of cofactors. However, it is not widely appreciated that antibodies are believed to be the major carrier protein in human circulation for the important riboflavin cofactor that is involved in a host of biological phenomena. A further link between riboflavin and antibodies was discovered 30 years ago when a bright-yellow antibody, IgG(GAR), was purified from a patient with multiple myeloma who had turned yellow during the course of her disease. It was subsequently shown that the yellow color of this antibody was due to riboflavin binding. However, it was not known how and where riboflavin was bound to this antibody. We now report the crystal structure of this historically important IgG(GAR) Fab at 3.0-A resolution. The riboflavin is located in the antigen-combining site with its isoalloxazine ring stacked between the parallel aromatic moieties of TyrH33, PheH58, and TyrH100A. Together with additional hydrogen bonds, these interactions reveal the structural basis for high-affinity riboflavin binding. The ligand specificity of IgG(GAR) is compared with another riboflavin-binding antibody, IgG(DOT), which was purified from a second patient with multiple myeloma. The crystal structure of IgG(GAR) provides a starting point for attempts to understand the physiological relevance and chemical functions of cofactor-containing antibodies.

Antibodies, Monoclonal↗
PubMed2006

Crystal structure of the IL-2 signaling complex: paradigm for a heterotrimeric cytokine receptor.

IL-2 is a cytokine that functions as a growth factor and central regulator in the immune system and mediates its effects through ligand-induced hetero-trimerization of the receptor subunits IL-2R alpha, IL-2R beta, and gamma(c). Here, we describe the crystal structure of the trimeric assembly of the human IL-2 receptor ectodomains in complex with IL-2 at 3.0 A resolution. The quaternary structure is consistent with a stepwise assembly from IL-2/IL-2R alpha to IL-2/IL-2R alpha/IL-2R beta to IL-2/IL-2R alpha/IL-2R beta/gamma(c). The IL-2R alpha subunit forms the largest of the three IL-2/IL-2R interfaces, which, together with the high abundance of charge-charge interactions, correlates well with the rapid association rate and high-affinity interaction of IL-2R alpha with IL-2 at the cell surface. Surprisingly, IL-2R alpha makes no contacts with IL-2R beta or gamma(c), and only minor changes are observed in the IL-2 structure in response to receptor binding. These findings support the principal role of IL-2R alpha to deliver IL-2 to the signaling complex and act as regulator of signal transduction. Cooperativity in assembly of the final quaternary complex is easily explained by the extraordinarily extensive set of interfaces found within the fully assembled IL-2 signaling complex, which nearly span the entire length of the IL-2R beta and gamma(c) subunits. Helix A of IL-2 wedges tightly between IL-2R beta and gamma(c) to form a three-way junction that coalesces into a composite binding site for the final gamma(c) recruitment. The IL-2/gamma(c) interface itself exhibits the smallest buried surface and the fewest hydrogen bonds in the complex, which is consistent with its promiscuous use in other cytokine receptor complexes.

Crystallography↗
PubMed2006

Antibody elbow angles are influenced by their light chain class.

We have examined the elbow angles for 365 different Fab fragments, and observe that Fabs with lambda light chains have adopted a wider range of elbow angles than their kappa chain counterparts, and that the lambda light chain Fabs are frequently found with very large (>195 degrees ) elbow angles. This apparent hyperflexibility of lambda chain Fabs may be due to an insertion in their switch region, which is one residue longer than in kappa chains, with glycine occurring most frequently at the insertion position. A new, web-based computer program that was used to calculate the Fab elbow angles is described.

Antibodies↗
PubMed2006

Complete reaction cycle of a cocaine catalytic antibody at atomic resolution.

Antibody 7A1 hydrolyzes cocaine to produce nonpsychoactive metabolites ecgonine methyl ester and benzoic acid. Crystal structures of 7A1 Fab' and six complexes with substrate cocaine, the transition state analog, products ecgonine methyl ester and benzoic acid together and individually, as well as heptaethylene glycol have been analyzed at 1.5-2.3 angstroms resolution. Here, we present snapshots of the complete cycle of the cocaine hydrolytic reaction at atomic resolution. Significant structural rearrangements occur along the reaction pathway, but they are generally limited to the binding site, including the ligands themselves. Several interacting side chains either change their rotamers or alter their mobility to accommodate the different reaction steps. CDR loop movements (up to 2.3 angstroms) and substantial side chain rearrangements (up to 9 angstroms) alter the shape and size (approximately 320-500 angstroms3) of the antibody active site from "open" to "closed" to "open" for the substrate, transition state, and product states, respectively.

Antibodies, Catalytic↗
PubMed2006

Enhanced major histocompatibility complex class I binding and immune responses through anchor modification of the non-canonical tumour-associated mucin 1-8 peptide.

Designing peptide-based vaccines for therapeutic applications in cancer immunotherapy requires detailed knowledge of the interactions between the antigenic peptide and major histocompatibility complex (MHC) in addition to that between the peptide-MHC complex and the T-cell receptor. Past efforts to immunize with high-affinity tumour-associated antigenic peptides have not been very immunogenic, which may be attributed to the lack of T cells to these peptides, having been deleted during thymic development. For this reason, low-to-medium affinity non-canonical peptides represent more suitable candidates. However, in addition to the difficulty in identifying such antigens, peptide binding to MHC, and hence its ability to induce a strong immune response, is limited. Therefore, to enhance binding to MHC and improve immune responses, anchor modifications of non-canonical tumour-associated peptides would be advantageous. In this study, the non-canonical tumour-associated peptide from MUC1, MUC1-8 (SAPDTRPA), was modified at the MHC anchor residues to SAPDFRPL (MUC1-8-5F8L) and showed enhanced binding to H-2Kb and improved immune responses. Furthermore, the crystal structure of MUC1-8-5F8L in complex with H-2Kb was determined and it revealed that binding of the peptide to MHC is similar to that of the canonical peptide OVA8 (SIINFEKL).

Animals↗
PubMed2006

Crystal structures of human immunodeficiency virus type 1 (HIV-1) neutralizing antibody 2219 in complex with three different V3 peptides reveal a new binding mode for HIV-1 cross-reactivity.

Human monoclonal antibody 2219 is a neutralizing antibody isolated from a human immunodeficiency virus type 1-infected individual. 2219 was originally selected for binding to a V3 fusion protein and can neutralize primary isolates from subtypes B, A, and F. Thus, 2219 represents a cross-reactive, human anti-V3 antibody. Fab 2219 binds to one face of the variable V3 beta-hairpin, primarily contacting conserved residues on the N-terminal beta-strand of V3, leaving the V3 crown or tip largely accessible. Three V3/2219 complexes reveal the antibody-bound conformations for both the N- and C-terminal regions that flank the V3 crown and illustrate how twisting of the V3 loop alters the relative dispositions and pairing of the amino acids in the adjacent V3 beta-strands and how the antibody can accommodate V3 loops with different sequences.

Antigen-Antibody Complex↗
PubMed2006

Structure-function analysis of the epitope for 4E10, a broadly neutralizing human immunodeficiency virus type 1 antibody.

The human immunodeficiency virus type 1 (HIV-1) neutralizing antibody 4E10 binds to a linear, highly conserved epitope within the membrane-proximal external region of the HIV-1 envelope glycoprotein gp41. We have delineated the peptide epitope of the broadly neutralizing 4E10 antibody to gp41 residues 671 to 683, using peptides with different lengths encompassing the previously suggested core epitope (NWFDIT). Peptide binding to the 4E10 antibody was assessed by competition enzyme-linked immunosorbent assay, and the K(d) values of selected peptides were determined using surface plasmon resonance. An Ala scan of the epitope indicated that several residues, W672, F673, and T676, are essential (>1,000-fold decrease in binding upon replacement with alanine) for 4E10 recognition. In addition, five other residues, N671, D674, I675, W680, and L679, make significant contributions to 4E10 binding. In general, the Ala scan results agree well with the recently reported crystal structure of 4E10 in complex with a 13-mer peptide and with our circular dichroism analyses. Neutralization competition assays confirmed that the peptide NWFDITNWLWYIKKKK-NH(2) could effectively inhibit 4E10 neutralization. Finally, to limit the conformational flexibility of the peptides, helix-promoting 2-aminoisobutyric acid residues and helix-inducing tethers were incorporated. Several peptides have significantly improved affinity (>1,000-fold) over the starting peptide and, when used as immunogens, may be more likely to elicit 4E10-like neutralizing antibodies. Hence, this study represents the first stage toward iterative development of a vaccine based on the 4E10 epitope.

Amino Acid Substitution↗
PubMed2006

How TCRs bind MHCs, peptides, and coreceptors.

Since the first crystal structure determinations of alphabeta T cell receptors (TCRs) bound to class I MHC-peptide (pMHC) antigens in 1996, a sizable database of 24 class I and class II TCR/pMHC complexes has been accumulated that now defines a substantial degree of structural variability in TCR/pMHC recognition. Recent determination of free and bound gammadelta TCR structures has enabled comparisons of the modes of antigen recognition by alphabeta and gammadelta T cells and antibodies. Crystal structures of TCR accessory (CD4, CD8) and coreceptor molecules (CD3epsilondelta, CD3epsilongamma) have further advanced our structural understanding of most of the components that constitute the TCR signaling complex. Despite all these efforts, the structural basis for MHC restriction and signaling remains elusive as no structural features that define a common binding mode or signaling mechanism have yet been gleaned from the current set of TCR/pMHC complexes. Notwithstanding, the impressive array of self, foreign (microbial), and autoimmune TCR complexes have uncovered the diverse ways in which antigens can be specifically recognized by TCRs.

Animals↗
PubMed2005

Structural basis for CD1d presentation of a sulfatide derived from myelin and its implications for autoimmunity.

Sulfatide derived from the myelin stimulates a distinct population of CD1d-restricted natural killer T (NKT) cells. Cis-tetracosenoyl sulfatide is one of the immunodominant species in myelin as identified by proliferation, cytokine secretion, and CD1d tetramer staining. The crystal structure of mouse CD1d in complex with cis-tetracosenoyl sulfatide at 1.9 A resolution reveals that the longer cis-tetracosenoyl fatty acid chain fully occupies the A' pocket of the CD1d binding groove, whereas the sphingosine chain fills up the F' pocket. A precise hydrogen bond network in the center of the binding groove orients and positions the ceramide backbone for insertion of the lipid tails in their respective pockets. The 3'-sulfated galactose headgroup is highly exposed for presentation to the T cell receptor and projects up and away from the binding pocket due to its beta linkage, compared with the more intimate binding of the alpha-glactosyl ceramide headgroup to CD1d. These structure and binding data on sulfatide presentation by CD1d have important implications for the design of therapeutics that target T cells reactive for myelin glycolipids in autoimmune diseases of the central nervous system.

Animals↗