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At least 19 recordsLinked to original sources
PubMed1989

Immunostimulatory activity of 1-O-acylated muramyl dipeptides, with or without a 6-O-phosphoryl group, in aqueous form.

Immunostimulatory effects of 1-O-acylated derivatives of N-acetyl-muramyl-L-alanyl-D-isoglutamine (MDP) methyl ester, with or without the 6-O-phosphoryl group, on augmentation of IgG antibody response against influenza hemagglutinin (HA) vaccine, in vivo macrophage activation and enhancement of non-specific host resistance against Pseudomonas aeruginosa infection were investigated. The activities were tested intraperitoneally (i.p.) in mice administered test samples solubilized or suspended in saline. The introduction of longer chain acyl groups into MDP methyl esters significantly induced enhancement of the IgG antibody response. Among them, the adjuvant activity of 1-O-linked 2-tetradecylhexadecanoyl (B30)-MDP methyl ester was comparable to that of 6-O-B30-MDP used as a positive control. Phosphorylation at the C6 position of the acylated MDP analogs did not induce a significant increment in the activity. With respect to phagocytic, cellular acid phosphatase and cytostasis-inducing activities, i.p. administration of acylated MDP analogs caused significant increment and activation of peritoneal macrophages. The cytostasis-inducing activity of 1-O-octadecanoyl- or 1-O-B30-MDP methyl ester with or without a phosphoryl group was more intensive than that of 6-O-B30-MDP. Acylated MDP analogs enhanced non-specific resistance against P. aeruginosa infection when the analogs were administered i.p. on the day before the infection. The enhancement was closely related to the accumulation of polymorphonuclear cells in the peritoneal cavity. The manifestation of these immunostimulatory activities by 1-O-acylated MDP analogs depended closely on the increasing carbon chain length of fatty acid substituents when administered in aqueous form.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1991

Solid-phase synthesis of a range of O-phosphorylated peptides by post-assembly phosphitylation and oxidation.

A completely general method for the O-phosphorylation of peptides of any given composition using solid-phase methodology is described. Peptides were assembled using Fmoc amino acid active esters, with base used for Fmoc deprotection. Unprotected amino acid side chain hydroxyl groups were phosphitylated and oxidised at the end of the assembly using bis(benzyloxy)(diisopropylamino)phosphine and tert.-butylhydroperoxide respectively. TFA was used for final deprotection of the amino acid side chains and for simultaneous cleavage from the resin. The synthesis of O-phosphopeptides of up to 15 residues in length is described.

Acylation↗
PubMed1977

2"-O-phosphorylation of gentamicin components by a Staphylococcus aureus strain carrying a plasmid.

A wild-type strain of Staphylococcus aureus that inactivates the 4,6-glycosidically linked deoxystreptamine aminoglycoside antibiotics by a plasmid-mediated process was found to harbor two enzymes: an acetyltransferase of the AAC(6') type and a new phosphotranferase specific to the gentamicin components. The target of this last enzyme is the 2''-hydroxyl function of these antibiotics, since one inactivated compound is 2''-(O)-phosphorylsisomicin.

Acetyltransferases↗
PubMed1991

Synthesis, NMR and function of an O-phosphorylated peptide, comprising the RGD-adhesion sequence of osteopontin.

The bone phosphoprotein osteopontin owes its cell adhesion property to the RGD-sequence. In order to determine whether a phosphate substituent on the serine following the RGD-sequence interferes with cell binding, we have synthesized GRGDSL along with the corresponding peptide phosphorylated on serine. The latter peptide showed significantly lower cell binding as measured by inhibition of adhesion of R1 cells to surfaces coated with BSP. GRGDSL and phosphorylated GRGDSL show NMR spectra which resemble each other more than that of GRGDSP derived from the fibronectin sequence.

Acetylglucosaminidase↗
PubMed1991

The binding specificity of high and low molecular weight phosphomannosyl receptors from bovine testes. Inhibition studies with chemically synthesized 6-O-phosphorylated oligomannosides.

A series of chemically synthesized oligomannosides that contain mannose 6-phosphate residues were utilized as inhibitors of the binding of beta-galactosidase to high (CI-MPR, 215 kDa) and low (CD-MPR, 41-46 kDa) molecular mass mannose 6-phosphate receptor from bovine testes in order to probe the specificity of each receptor. Mannobioside phosphorylated in the terminal position and linked alpha(1,2) was a 6-fold better inhibitor than the corresponding alpha(1,3)- and alpha (1,6)-linked isomers. Inhibition observed with a monophosphorylated alpha(1,2)-linked mannotrioside was approximately 6-fold greater than that with the corresponding mannobioside. Penultimate glycosidic linkages of the oligomannosides played little or no role in the inhibition of binding of ligand to the receptors. Monophosphorylated oligomannosides containing phosphomonoester groups on penultimate mannose residues were not inhibitors. Binding inhibition observed for biantennary oligomannosides with phosphate on terminal mannose residues of either alpha(1,3) or alpha(1,6) chains closely approximated the values obtained with analogous trimannosides. A biantennary oligomannoside on which each antennary chain contained a terminal phosphate exhibited approximately an 8-fold greater inhibition than monophosphorylated compounds. Although the receptors exhibited similar relative specificities for phosphomonoesters, phosphodiesters did not inhibit binding of ligand to CD-MPR and only weakly inhibited binding to CI-MPR.

Animals↗
PubMed1979

Synthesis and chemical properties of N- and O-phosphorylated derivatives of creatinol.

N-Methyl-N-(beta-hydroxyethyl)-guanidine O-phosphate (creatinol O-phosphate) was synthesized from creatinol by phosphorylation with partially hydrolyzed phosphoryl chloride or by dehydration of its phosphate salt. Creatinol N-phosphate was obtained by addition of N-methylamino ethanol to bis-p-nitrobenzylphosphocyanamide, followed by hydrogenolysis. The chemical properties of both compounds were investigated; creatinol N-phosphate was rearranged to creatinol O-phosphate by heating.

Chemical Phenomena↗
PubMed1986

Structural requirements for inducing in vitro B lymphocyte activation by chemically synthesized derivatives related to the nonreducing D-glucosamine subunit of lipid A.

Mitogenic and polyclonal B cell activation (PBA) activities of 16 synthetic compounds related to the nonreducing D-glucosamine (GlcN-II) subunit of lipid A were investigated. Among compounds possessing the GlcN backbone, a 4-O-phosphorylated GlcN derivative carrying N-linked 3-tetradecanoyloxytetradecanoyl [C14-O-(C14)] and 3-O-linked tetradecanoyl (C14) groups, GLA-27, expressed the highest degree of both activities. Omission of the 3-O-linked C14 group from GLA-27 and transfer of the C14 group to the C-6 position induced critical changes in expression of activities. Both 4-O-phosphorylated compounds carrying an N-linked C14 or 3-hydroxytetradecanoyl (C14OH) group instead of the C14-O-(C14) group in GLA-27 showed no detectable activity. Substituting a 3-O-linked C14 group in GLA-27 for the C14-O-(C14) group also markedly decreased mitogenic and PBA activities. Change of phosphorylation site from the C-4 to the C-6 position and bisphosphorylation at the C-4 and C-6 positions induced somewhat weak depression. Much weaker activities were observed in a compound carrying N-linked 3-dodecanoyloxydodecanoyl [C12-O-(C12)] and 3-O-dodecanoyl (C12) as fatty acid substituents. No detectable activity was seen in a compound carrying N-linked 3-hexadecanoyloxyhexadecanoyl [C16-O-(C16)] and 3-O-hexadecanoyl (C16), indicating that the most suitable carbon chain length for expressing the activities is C14. Regarding structural change of the GlcN backbone, a 1-deoxy derivative of GLA-27 exhibited stronger activity than did GLA-27 itself. Mitogenic and PBA activity of GLA-27 were stronger than those of lipid X, which corresponds to the reducing D-GlcN (GlcN-I) subunit of Escherichia coli lipid A and is a 1-O-phosphorylated GlcN derivative carrying N- and 3-O-linked C14OH groups. These results indicate that N-linked acyloxyacyl and 3-O-linked acyl groups and phosphorylation are critical for expressing both mitogenic and PBA activities.

Animals↗
PubMed1989

Antibodies and radioimmunoassays for phosphoserine, phosphothreonine and phosphotyrosine. Serologic specificities and levels of the phosphoamino acids in cytoplasmic fractions of rat tissues.

For antibody production, the O-phosphorylated derivative of tyrosine, threonine, or serine was covalently linked to succinylated bovine albumin via the carbodiimide reaction. Each conjugate was then complexed with methylated bovine albumin for immunization of rabbits. To determine binding, the corresponding O-phosphorylated [3H]amino acids were chemically synthesized. In addition, these 3H-phosphorylated derivatives were acylated (with succinic or acetic anhydride) to obtain ligands whose structures resemble those present in the immunogen. The acylated ligands bound to their respective antibodies more effectively: in some cases binding was about three orders of magnitude greater than their non-acylated counterparts. Radioimmunoassays were therefore developed using the N-succinyl-[3H]phosphoamino acids. When the unlabeled N-succinyl-phosphorylated amino acids were used as inhibitors in the homologous immune systems, 50% displacement of the labeled ligand was found with 0.06, 0.27 or 0.8 pmol of the tyrosine, threonine, or serine derivative, respectively. The antibodies were highly specific for the homologous hapten; the requirement for the phosphate group on the acylated amino acid was essentially absolute. Antibody content (expressed as mg/ml serum) and apparent binding constants for the N-succinyl derivatives in individual bleedings of immune sera were 1.9 and 1 X 10(10) M-1 for phosphotyrosine, 0.825 and 6 X 10(8) M-1 for phosphothreonine, and 0.150 and 2 X 10(8) M-1 for phosphoserine. The radioimmunoassays were used to quantitate the phosphoamino acids in cytoplasmic fractions of rat tissue extracts. The production of antibodies to phosphorylated O-tyrosine has been reported previously, but to our knowledge, this represents the first report of antibodies specific for O-phosphorylated serine and threonine residues.

Animals↗
PubMed1989

[Chemical properties of lipopolysaccharide (LPS) isolated from Vibrio anguillarum PT514].

Vibrio anguillarum, one of the causative agents of fish vibriosis, is serologically and biochemically divided into three groups (A, B and C). The chemical composition and molecular architecture of lipopolysaccharide (LPS) isolated from V. anguillarum PT 514, which belongs to serogroup B, were investigated. The LPS contained glucose (Glc), fructose (Fru), L-glycero-D-mannoheptose (L-D Hep), glucosamine (GlcN) and 4-amino-4,6-dideoxyglucose as sugar constituents in molar ratios of 8.9:0.7:3.0:1.1:1.6. Sephadex G-50 gel-chromatography of a degraded polysaccharide fraction separated from the LPS by 5% acetic acid hydrolysis suggested that the O-specific polysaccharide region consists of, in average, as much as 29 moles of Glc per 3 moles of L-D Hep, while the core polysaccharide contains at least Glc, L-D Hep and GlcN in molar ratios of 3.2 : 3.0 : 0.2. Fru and 4-amino-4,6-dideoxyglucose components were released from LPS on weak-acid hydrolysis, indicating that PT 514 LPS is distinguishable from those of Vibrio anguillarum belonging to the other serogroups. 2-Keto-3-deoxyoctonate (KDO), a common sugar constituent of gram-negative bacterial LPS, was not detected by Weissbach's color reaction under the conventional hydrolysis condition, but O-phosphoryl KDO was found in the strong-acid hydrolysate (4 M HCl, 100 C, 45 min). This substance was identical, at least in high-voltage paper electrophoresis, to 5-O-phosphoryl KDO.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrates↗
PubMed2026

Integrative proteomics and bioinformatics pipelines for PTM profiling.

Post-translational modifications (PTMs) regulate protein function across all life forms and allow plants to respond rapidly to biotic and abiotic stress. Over 450 PTM types have been described across organisms, of which 23-33 have been experimentally confirmed in plants, including phosphorylation, acetylation, methylation, glycosylation, ubiquitination, and sumoylation. These modifications are highly dynamic and often reversible, and frequently act in combination, or "crosstalk," to fine-tune cellular processes. Advances in high-resolution mass spectrometry and large-scale genome sequencing continue to expand the catalogue of known PTM sites, while machine learning and deep learning approaches increasingly support prediction of PTM site localization and function. Unlike broader surveys of plant PTMs, this review focuses specifically on O-phosphorylation and Lys-N(ε)-acetylation, the two best-characterized and most extensively crosstalking PTMs in plants, and integrates four perspectives: the historical development of proteomic and bioinformatics approaches to these modifications; current mass spectrometry-based workflows and enrichment strategies; the bioinformatics tools and databases available for their analysis; and the technical and species-related challenges, particularly in non-model plants, that currently limit their study. We close by outlining priority directions for future research, including multi-omics integration, AI-based prediction, and the translation of PTM knowledge into crop stress resilience and breeding applications.

Protein Processing, Post-Translational↗
PubMed1975

Phosphatidylkojibiosyl Diglyceride: metabolism and function as an anchor in bacterial cell membrane.

The recently discovered phosphoglycolipid, phosphatidylkojibiosyl diglyceride (PKD), was first observed as a biosynthetic by-product of glycosyl diglyceride metabolism in Streptococcus faecalis (faecium) ATCC 9790. Its structure is 1, 2-diacyl-3-O-alpha-Dglucopyranosyl-6'-O-phosphoryl- [1'', 2''-diacyl-3''-O-sn-glycerol]-alpha-D-glucopyranosyl)-sn-glycerol. The biosynthesis of phosphatidyl-kojibiosyl diglyceride occurs by a novel transphosphatidylation reaction in which a phosphatidyl glycerol to the primary alcohol function at the 6 position of the internal glucose of kojibiosyl diglyceride. The reaction is catalyzed by a membrane-derived enzyme. Phosphatidyl-kojibiosyl diglyceride is bound covalently through a phosphodiester bond to the polyglycerol phosphate moiety of membrane lipoteichoic acid from S. faecalis. Phosphatidylkojibiosyl diglyceride has four nonpolar long chain fatty acyl groups and appears to have the necessary physico-chemical properties to anchor the long hydrophilic glycerol phosphate polymer of lipoteichoic acid to the hydrophobic enviroment of the membrane of S. faecalis and probably other gram-positive bacteria as well.

Cell Membrane↗
PubMed1991

C-glycosidic analogues of lipid A and lipid X: synthesis and biological activities.

The synthesis of a series of novel analogues of lipid A, the lipophilic terminal of lipopolysaccharides (LPS), and lipid X, the reducing monosaccharide unit in lipid A, is reported. In these compounds, the native 1-O-phosphate group has been replaced by a "bioisosteric" CH2COOH substituent. The new N,O-acylated monosaccharide C-glycosides were obtained by Wittig reaction of suitably protected glucosamine derivatives. These lipid X analogues were recognized as substrates by the enzyme lipid A synthase and could be coupled with UDP-lipid X to afford the corresponding disaccharide analogues of the lipid A precursor on preparative scale. All compounds were characterized by NMR, MS, and elemental analysis, and were tested for their ability to enhance nonspecific resistance to infection in mice and also for endotoxicity. The results clearly show that the new compounds express biological activities similar to those of their O-phosphorylated natural counterparts. Furthermore, these compounds exhibit a better therapeutic index in mouse models than the standard LPS obtained from Salmonella abortus equi.

Animals↗
PubMed1990

Characterization of 3'-phosphoadenosine 5'-phospho[35S]sulfate transport carrier from rat brain microsomes.

3'-Phosphoadenosine 5'-phospho[35S]sulfate [( 35S]PAPS) specific binding properties of rat brain tissue were studied. [35S]PAPS specific binding was optimal at pH 5.8 in either Tris-maleate or potassium phosphate buffers. Association was maximal at low temperature, reaching equilibrium in 20 min. Dissociation was rapid, with a dissociation time of 80 s. Scatchard analysis of [35S]PAPS specific binding was consistent with a single site having a KD of 0.46 +/- 0.06 microM and a Bmax of 20.8 +/- 2.0 pmol/mg of protein. Low concentrations of Triton X-100 (0.025%) were effective in increasing the number of binding sites to a Bmax of 44.5 +/- 4.6 pmol/mg of protein without affecting the affinity. [35S]PAPS specific binding was enriched in crude synaptic membranes (P2) and microsomes (P3). Regional distribution of [35S]PAPS specific binding was quite homogeneous in all brain structures studied. The pharmacological profile of [35S]PAPS specific binding in rat brain microsomes was consistent with a membrane protein having a high selectivity for the 3'-O-phosphoryl group substitution on the ribose moiety. Thus, 3'-phosphoadenosine 5'-phosphate was more potent than 2'-phosphoadenosine 5'-phosphate in competing for [35S]PAPS specific binding. Adenosine 5'-phosphosulfate was a good inhibitor of [35S]PAPS specific binding. ATP and ADP were also good displacers. Dipyridamole, a highly selective marker for adenosine uptake sites, was ineffective. 4,4-Diisothiocyanostilbene-2,2-disulfonic acid, the chloride transporter inhibitor, showed an IC50 of 36 +/- 5.1 microM for inhibition of [35S]PAPS specific binding. 2,6-Dichloro-4-nitrophenol had a low selectivity in competing for the [35S]PAPS binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1975

Human liver acid phosphatases.

Human liver contains three chromatographically distinct forms of non-specific acid phosphatase (EC 3.1.3.2). Acid phosphatases I, II and III have molecular weights of greater than 200 000, of 107 000, and of 13 400, respectively. Following partial purification, isoenzyme II was obtained as a single activity band, as assessed by activity staining with p-nitrophenyl phosphate and alpha-naphthyl phosphate on polyacrylamide gels run at several pH values. With 50mM p-nitrophenyl phosphate as a substrate, enzymes II and III exhibit plateaus of activity over the pH range 3 - 5 and 3.5 - 6, respectively. Acid phosphatase II is not significantly inhibited by 0.5% formaldehyde. The activity of human liver acid phosphatase II and of human prostatic acid phosphatase towards several substrates is compared. The liver enzyme, is marked contrast to the prostatic enzyme, does not hydrolyze O-phosphoryl choline.

Acid Phosphatase↗
PubMed1990

Insulin-receptor tyrosine kinase and glucose transport.

We identified the earliest events in autophosphorylation of the insulin receptor after insulin addition. Insulin-stimulated autophosphorylation at specific sites in the tyrosine kinase domain of the receptor's beta-subunit is correlated kinetically with activation of kinase-catalyzed phosphorylation of a model substrate (reduced and carboxyamidomethylated lysozyme; RCAM-lysozyme). To identify these sites, the deduced amino acid sequence of the 3T3-L1 adipocyte insulin receptor of the mouse was determined. Insulin-induced activation of substrate phosphorylation was shown to require autophosphorylation of three neighboring tyrosines (Tyr1148, Tyr1152, and Tyr1153) in the mouse receptor. A search for cellular substrates of the receptor kinase revealed that insulin causes accumulation of a 15,000-Mr phosphorylated (on tyrosine) cytosolic protein (pp15) in 3T3-L1 adipocytes treated with oxophenylarsine (PAO). PAO blocks turnover of the phosphoryl group of pp15, causing its accumulation, and thereby appears to interrupt signal transmission from the receptor to the glucose-transport system. Two membrane-bound protein phosphotyrosine phosphatases that are inhibited by PAO and are apparently responsible for the turnover of the pp15 phosphoryl group have been purified from 3T3-L1 adipocytes and characterized. These and other results support the hypothesis that turnover of the phosphoryl group of pp15, a product of insulin-receptor tyrosine kinase action, couples signal transmission to the glucose-transport system. [32P]pp15 was purified to homogeneity from 3T3-L1 adipocytes. Amino acid and radiochemical sequence analysis of the purified tryptic [32P]phosphopeptide revealed that pp15 is the phosphorylation product of 422(aP2) protein, a 15,000-Mr adipocyte protein whose cDNA we previously cloned and sequenced. 422(aP2) protein was found to bind fatty acids. When exposed to a free fatty acid, notably oleic acid, 422(aP2) protein becomes an excellent substrate of the isolated insulin-receptor tyrosine kinase. Compelling evidence indicates that on binding fatty acid, 422(aP2) protein undergoes a conformational change whereby Tyr19 becomes accessible to the receptor tyrosine kinase and undergoes O-phosphorylation. Adipose tissue and skeletal and heart muscle, which exhibit insulin-stimulated glucose uptake, express a specific insulin-responsive glucose transporter. A cDNA (GT2) that encodes this protein was isolated from a mouse 3T3-L1 adipocyte library and sequenced. We also isolated and characterized the corresponding mouse gene GLUT4. DNase I footprinting with nuclear extracts from 3T3-L1 cells revealed that a differentiation-specific nuclear factor binds to the GLUT4 promoter. The purified transcription factor C/EBP binds at the same position.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

[Site-directed chemical restriction of a single-stranded DNA fragment by an alkylating derivative of the tetranucleotide d(pApGpCpA) in the presence of tetranucleotide effectors].

Alkylation of a single-stranded DNA 302-mer by a 5'-O-phosphoryl-[4-(N-2-chloroethyl-N-methylamino)benzyl]amide derivative of the tetradeoxyribonucleotide d(pApGpCpA) in the presence of 3',5'-di-N-(2-hydroxyethyl) phenazinium derivatives of tetranucleotides as effectors led to specific chemical cleavage of the target at the guanosine residues of the sites ... pTpGppT. The reagent can be selectively addressed to one of three alkylation sites with the aid of a pair of tetranucleotide effectors flanking the chemically reactive tetranucleotide in the complex with the target DNA. The yield of the cleavage depends on the concentration of both the reagent and effectors, and can be enhanced, if a chain of two or more effectors from each side of the reagent is used. In this case, 3',5'-di-Phn-tetranucleotide effectors are to immediately flank the reagent.

Alkylation↗