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Phosphorylcholine esterase is critical for Dolichos biflorus and Helix pomatia agglutinin binding to pneumococcal teichoic acid.

ABSTRACT: Streptococcus pneumoniae (the pneumococcus) has wall teichoic acid (WTA) and lipoteichoic acid (LTA) expressing the Forssman antigen (FA). Two lectins, Dolichos biflorus agglutinin (DBA) and Helix pomatia agglutinin (HPA), are known to bind FA. To determine the molecular structure targeted by these two lectins, different pneumococcal strains were studied for DBA/HPA binding with flow cytometry and fluorescence microscopy. Genetic experiments were used to further examine the lectins' molecular target. Twelve strains were positive for DBA binding, whereas three were negative. Super-resolution microscopy showed that DBA stained only the subcapsular area of pneumococci. The three DBA nonbinders showed no phosphorylcholine esterase (Pce) activity in vitro, whereas 10 DBA binders displayed Pce activity (the remaining two strains were DBA binders with no Pce activity in vitro). The pcegene sequence for 10 representative strains revealed two functional pce alleles, the previously recognized "allele A" and a newly discovered "allele B" (with 12 additional nucleotides). Isolates with allele B showed no Pce activity in vitro but did bind to DBA, indicating allele B Pce is functional in vivo. Genetic transfer experiments confirmed that either allele is sufficient (and necessary) for DBA binding. The three DBA nonbinders had various mutations that affected Pce function. Observations with HPA were identical to those with DBA. We show that DBA and HPA bind only to the WTA/LTA of pneumococcal isolates with a functional Pce enzyme. A newly discovered Pce variant (allele B) is functional in vivo but nonfunctional when assayed in vitro.

SUBMITTER: Zhou ML

PROVIDER: S-EPMC7676324 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Attachment of phosphorylcholine residues to pneumococcal teichoic acids and modification of substitution patterns by the phosphorylcholine esterase.

Project description:The bacterial lung pathogen Streptococcus pneumoniae has a unique nutritional requirement for exogenous choline and attaches phosphorylcholine (P-Cho) residues to the GalpNAc moieties of its teichoic acids (TAs) in its cell wall. Two phosphorylcholine transferases, LicD1 and LicD2, mediate the attachment of P-Cho to the O-6 positions of the two GalpNAc residues present in each repeating unit of pneumococcal TAs (pnTAs), of which only LicD1 has been determined to be essential. At the molecular level, the specificity of the P-Cho attachment to pnTAs by LicD1 and LicD2 remains still elusive. Here, using detailed structural analyses of pnTAs from a LicD2-deficient strain, we confirmed the specificity in the attachment of P-Cho residues to pnTA. LicD1 solely transfers P-Cho to α-d-GalpNAc moieties, whereas LicD2 attaches P-Cho to β-d-GalpNAc. Further, we investigated the role of the pneumococcal phosphorylcholine esterase (Pce) in the modification of the P-Cho substitution pattern of pnTAs. To clarify the specificity of Pce-mediated P-Cho hydrolysis, we evaluated different concentrations and pH conditions for the treatment of pneumococcal lipoteichoic acid with purified Pce. We show that Pce can hydrolyze both P-Cho residues of the terminal repeat of the pnTA chain and almost all P-Cho residues bound to β-d-GalpNAc in vitro However, hydrolysis in vivo was restricted to the terminal repeat. In summary, our findings indicate that LicD1 and LicD2 specifically transfer P-Cho to α-d-GalpNAc and β-d-GalpNAc moieties, respectively, and that Pce removes distinct P-Cho substituents from pnTAs.

| S-EPMC6036202 | biostudies-literature

Crystallization and preliminary X-ray diffraction studies of the pneumococcal teichoic acid phosphorylcholine esterase Pce.

Project description:The pneumococcal phosphorylcholine esterase (Pce or CbpE) is a modular protein that hydrolyses the phosphorylcholine residues present in the teichoic and lipoteichoic acids of the pneumococcal cell wall. Pce has been crystallized using the hanging-drop vapour-diffusion method at 291 K. Diffraction-quality monoclinic crystals belong to space group C2, with unit-cell parameters a = 169.82, b = 57.26, c = 67.44 A, beta = 112.60 degrees. A 2.7 A resolution SAD data set from a non-isomorphous Gd-HPDO3A Pce derivative was collected at the gadolinium L(III) absorption edge using synchrotron radiation.

| S-EPMC1952259 | biostudies-literature

Identification of O-Linked Glycoproteins Binding to the Lectin Helix pomatia Agglutinin as Markers of Metastatic Colorectal Cancer.

Project description:Protein glycosylation is an important post-translational modification shown to be altered in all tumour types studied to date. Mucin glycoproteins have been established as important carriers of O-linked glycans but other glycoproteins exhibiting altered glycosylation repertoires have yet to be identified but offer potential as biomarkers for metastatic cancer.In this study a glycoproteomic approach was used to identify glycoproteins exhibiting alterations in glycosylation in colorectal cancer and to evaluate the changes in O-linked glycosylation in the context of the p53 and KRAS (codon 12/13) mutation status. Affinity purification with the carbohydrate binding protein from Helix pomatia agglutinin (HPA) was coupled to 2-dimensional gel electrophoresis with mass spectrometry to enable the identification of low abundance O-linked glycoproteins from human colorectal cancer specimens.Aberrant O-linked glycosylation was observed to be an early event that occurred irrespective of the p53 and KRAS status and correlating with metastatic colorectal cancer. Affinity purification using the lectin HPA followed by proteomic analysis revealed annexin 4, annexin 5 and CLCA1 to be increased in the metastatic colorectal cancer specimens. The results were validated using a further independent set of specimens and this showed a significant association between the staining score for annexin 4 and HPA and the time to metastasis; independently (annexin A4: Chi square 11.45, P = 0.0007; HPA: Chi square 9.065, P = 0.0026) and in combination (annexin 4 and HPA combined: Chi square 13.47; P = 0.0002).Glycoproteins showing changes in O-linked glycosylation in metastatic colorectal cancer have been identified. The glycosylation changes were independent of p53 and KRAS status. These proteins offer potential for further exploration as biomarkers and potential targets for metastatic colorectal cancer.

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Helix pomatia

Project description:Helix pomatia Assembly

| PRJNA311081 | ENA

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Project description:Helix pomatia overview

| PRJNA528132 | ENA

Pneumococcal phosphorylcholine esterase, Pce, contains a metal binuclear center that is essential for substrate binding and catalysis.

Project description:The phosphorylcholine esterase from Streptococcus pneumoniae, Pce, catalyzes the hydrolysis of phosphorylcholine residues from teichoic and lipoteichoic acids attached to the bacterial envelope and comprises a globular N-terminal catalytic module containing a zinc binuclear center and an elongated C-terminal choline-binding module. The dependence of Pce activity on the metal/enzyme stoichiometry shows that the two equivalents of zinc are essential for the catalysis, and stabilize the catalytic module through a complex metal-ligand coordination network. The pH dependence of Pce activity toward the alternative substrate p-nitrophenylphosphorylcholine (NPPC) shows that k(cat) and k(cat)/K(m) depend on the protonation state of two protein residues that can be tentatively assigned to the ionization of the metal-bound water (hydrogen bonded to D89) and to H228. Maximum activity requires deprotonation of both groups, although the catalytic efficiency is optimum for the single deprotonated form. The drastic reduction of activity in the H90A mutant, which still binds two Zn2+ ions at neutral pH, indicates that Pce activity also depends on the geometry of the metallic cluster. The denaturation heat capacity profile of Pce exhibits two peaks with T(m) values of 39.6 degrees C (choline-binding module) and 60.8 degrees C (catalytic module). The H90A mutation reduces the high-temperature peak by about 10 degrees C. Pce is inhibited in the presence of 1 mM zinc, but this inhibition depends on pH, buffer, and substrate species. A reaction mechanism is proposed on the basis of kinetic data, the structural model of the Pce:NPPC complex, and the currently accepted mechanism for other Zn-metallophosphoesterases.

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Fluorescence Imaging of Streptococcus pneumoniae with the Helix pomatia agglutinin (HPA) As a Potential, Rapid Diagnostic Tool.

Project description:Streptococcus pneumoniae is a common human pathogen and a major causal agent of life-threatening infections that can either be respiratory or non-respiratory. It is well known that the Helix pomatia (edible snail) agglutinin (HPA) lectin shows specificity for terminal ?GalNAc residues present, among other locations, in the Forssman pentasaccharide (?GalNAc1?3?GalNAc1?3?Gal1?4?Gal1?4?Glc). Based on experiments involving choline-independent mutants and different growth conditions, we propose here that HPA recognizes the ?GalNAc terminal residues of the cell wall teichoic and lipoteichoic acids of S. pneumoniae. In addition, experimental evidence showing that pneumococci can be specifically labeled with HPA when growing as planktonic cultures as well as in mixed biofilms of S. pneumoniae and Haemophilus influenzae has been obtained. It should be underlined that pneumococci were HPA-labeled despite of the presence of a capsule. Although some non-pneumococcal species also bind the agglutinin, HPA-binding combined with fluorescence microscopy constitutes a suitable tool for identifying S. pneumoniae and, if used in conjunction with Gram staining and/or other suitable technique like antigen detection, it may potentially facilitate a fast and accurate diagnosis of pneumococcal infections.

| S-EPMC5513899 | biostudies-literature

Evolution of Cd2+ and Cu+ binding in Helix pomatia metallothioneins.

Project description:Metallothioneins (MTs) are small proteins present in all kingdoms of life. Their high cysteine content enables them to bind metal ions, such as Zn2+, Cd2+, and Cu+, providing means for detoxification and metal homeostasis. Three MT isoforms with distinct metal binding preferences are present in the Roman Snail Helix pomatia. Here, we use nuclear magnetic resonance (NMR) to follow the evolution of Cd2+ and Cu+ binding from the reconstructed ancestral Stylommatophora MT to the three H. pomatia MT (HpMT) isoforms. Information obtained from [15N,1H]-HSQC spectra and T2 relaxation times are combined to describe the conformational stability of the MT-metal complexes. A well-behaved MT-metal complex adopts a unique structure and does not undergo additional conformational exchange. The ancestor to all three HpMTs forms conformationally stable Cd2+ complexes and closely resembles the Cd2+-specific HpCdMT isoform, suggesting a role in Cd2+ detoxification for the ancestral protein. All Cu+-MT complexes, including the Cu+-specific HpCuMT isoform, undergo a considerable amount of conformational exchange. The unspecific HpCd/CuMT and the Cu+-specific HpCuMT isoforms form Cu+ complexes with comparable characteristics. It is possible to follow how Cd2+ and Cu+ binding changed throughout evolution. Interestingly, Cu+ binding improved independently in the lineages leading to the unspecific and the Cu+-specific HpMT isoforms. C-terminal domains are generally less capable of coordinating the non-cognate metal ion than N-terminal domains, indicating a higher level of specialization of the C-domain. Our findings provide new insights into snail MT evolution, helping to understand the interplay between biological function and structural features toward a comprehensive understanding of metal preference.

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Project description:Helix pomatia agglutinin (HPA), the lectin from the albumen gland of the Roman snail, has been used in histochemical studies relating glycosylation changes to the metastatic potential of solid tumors. To facilitate the use of HPA in a clinical (diagnostic) setting, detailed analysis of the lectin, including cloning and recombinant production of HPA, is required. A combination of isoelectric focusing, amino acid sequence analysis, and cloning revealed two polypeptides in native HPA preparations (HPAI and HPAII), both consistent with GalNAc-binding lectins of the H-type family. Pairwise sequence alignment showed that HPAI and HPAII share 54% sequence identity whereas molecular modeling using SWISS-MODEL suggests they are likely to adopt similar tertiary structure. The inherent heterogeneity of native HPA highlighted the need for production of functional recombinant protein; this was addressed by preparing His-thioredoxin-tagged fusion products in Escherichia coli Rosetta-gami B (DE3) cells. The recombinant lectins agglutinated human blood group A erythrocytes whereas their oligosaccharide specificity, evaluated using glycan microarrays, showed that they predominantly bind glycans with terminal ?-GalNAc residues. Surface plasmon resonance with immobilized GalNAc-BSA confirmed that recombinant HPAI and HPAII bind strongly with this ligand (K(d) = 0.60 nm and 2.00 nm, respectively) with a somewhat higher affinity to native HPA (K(d) = 7.67 nm). Recombinant HPAII also bound the breast cancer cells of breast cancer tissue specimens in a manner similar to native lectin. The recombinant HPA described here shows important potential for future studies of cancer cell glycosylation and as a reagent for cancer prognostication.

| S-EPMC3121508 | biostudies-literature

Does Variation of the Inter-Domain Linker Sequence Modulate the Metal Binding Behaviour of Helix pomatia Cd-Metallothionein?

Project description:Snail metallothioneins (MTs) constitute an ideal model to study structure/function relationships in these metal-binding polypeptides. Helix pomatia harbours three MT isoforms: the highly specific CdMT and CuMT, and an unspecific Cd/CuMT, which represent paralogous proteins with extremely different metal binding preferences while sharing high sequence similarity. Preceding work allowed assessing that, although, the Cys residues are responsible for metal ion coordination, metal specificity or preference is achieved by diversification of the amino acids interspersed between them. The metal-specific MT polypeptides fold into unique, energetically-optimized complexes of defined metal content, when binding their cognate metal ions, while they produce a mixture of complexes, none of them representing a clear energy minimum, with non-cognate metal ions. Another critical, and so far mostly unexplored, region is the stretch linking the individual MT domains, each of which represents an independent metal cluster. In this work, we have designed and analyzed two HpCdMT constructs with substituted linker segments, and determined their coordination behavior when exposed to both cognate and non-cognate metal ions. Results unequivocally show that neither length nor composition of the inter-domain linker alter the features of the Zn(II)- and Cd(II)-complexes, but surprisingly that they influence their ability to bind Cu(I), the non-cognate metal ion.

| S-EPMC4730253 | biostudies-literature

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