Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Mannosephosphates”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1989

Multifunctional glycoprotein receptors for insulin and the insulin-like growth factors.

Insulin and the insulin-like growth factors (IGF) I and II are structurally related peptides that elicit a large number of similar biological effects in target cells. Three well-characterized receptor complexes bind one or more of these peptides with high affinity. Two of these receptors, denoted as type I, are ligand-activated tyrosine kinases with similar heterotetrameric alpha 2 beta 2 subunit structures which bind insulin or IGF-I, respectively, with highest affinity. Ligand-stimulated tyrosine autophosphorylation of these receptors further activates their intrinsic tyrosine kinase activities both in vitro and in intact cells. Rapid signal transduction follows such receptor autophosphorylation and tyrosine kinase activation, leading to increased serine phosphorylation of many cellular proteins and decreased serine phosphorylation of several others. Experiments in our laboratory have identified three distinct insulin-activated serine kinase activities in cell-free extracts that appear to account for the insulin-stimulated serine phosphorylation of the insulin receptor itself, ATP citrate lyase, and acetyl CoA carboxylase, respectively. A third receptor in this group binds IGF-I and II, lacks kinase activity and is denoted as type II IGF receptor. Amino acid sequences of this receptor deduced from isolated rat cDNA clones show a high degree of homology with those of the bovine cation-independent mannose 6-phosphate (Man-6-P) receptor. We demonstrated that these receptors are indeed identical. The IGF-II/Man-6-P receptor rapidly recycles between the cell surface membrane and intracellular membrane compartments, providing for the rapid uptake of both IGF-II and mannose 6-phosphate-linked lysosomal enzymes. Insulin action markedly increases the proportion of receptors in the plasma membrane and the uptake of bound ligands. We also observe that large amounts of the extracellular domain of the IGF-II/Man-6-P receptor are released into the serum of fetal, neonatal and adult rats. The biological role of this receptor in IGF-II function is yet to be determined.

Animals↗
PubMed1989

Molecular mechanisms of bone resorption by the osteoclast.

The osteoclast is a multinucleated cell that is actively engaged in the synthesis of lysosomal enzymes, their vectorial transport toward the apical membrane, and the secretion of these enzymes at its apical pole. These secreted enzymes are targeted to the apical ruffled-border membrane by mechanisms that involve cation-independent mannose-6-phosphate receptors. These receptors bind to an enzyme-linked mannose-6-phosphate recognition marker in the Golgi complex, and the enzyme-ligand-receptor complex, carried within small coated transport vesicles, dissociates upon reaching the low pH established in the bone-resorbing compartment by the osteoclast. The apical bone-resorbing compartment is sealed off by the attachment of the osteoclast to the calcified matrix and is actively acidified by the osteoclast. The plasma membrane of the cell is divided into distinct domains. The apical membrane at the ruffled-border shares common antigenic determinants with lysosomal and endosomal membranes, including a 100 kD protein and proton pumps that may be involved in the acidification of the extracellular resorbing compartment. The basolateral membrane is highly enriched in carbonic anhydrase, and bicarbonate-chloride exchange appears to regulate the intracellular pH of this cell. These observations are consistent with a scheme in which, in the low pH environment of the bone-resorbing lacuna produced by the osteoclast, the mineral phase dissolves, exposing the organic matrix to the action of the secreted enzymes. The activity of these enzymes is in turn presumably favored by the acidic milieu. All constituents of the matrix, whether mineral or organic, then would be reduced to their elemental forms (ions and amino acids) extracellularly.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Phosphatase↗
PubMed1992

Evidence that mannose recognition by splenic sinusoidal cells plays a role in the splenic entry of lymphocytes.

Previous studies demonstrated that mannan is a potent inhibitor of splenic entry of lymphocytes and mediates its inhibitory effect at an unidentified site in the spleen rather than acting directly on lymphocytes. This report describes the in vivo site of action of mannan. In vivo localization studies with fluoresceinated preparations of mannan (Fl-mannan) and a mannose-6-phosphate-containing yeast phosphomannan monoester core from P. holstii exopolysaccharide (Fl-PPME) demonstrated that the polysaccharide specifically localize in the splenic marginal sinuses in cells with a dendritic morphology termed splenic sinusoidal cells (SSC). Uptake of the polysaccharides by SSC was mediated by a mannan-specific receptor which was saturable and of high avidity. Several lines of evidence suggested that mannan uptake by SSC inhibited splenic entry of lymphocytes. First, the ability of SSC to bind Fl-mannan and Fl-PPME closely paralleled the ability of these polysaccharides to inhibit splenic entry of lymphocytes. In fact, doses of mannan and PPME which would saturate SSC mannan receptors completely blocked splenic entry of lymphocytes. Second, SSC are situated at the initial entry point of lymphocytes into spleen and passage of lymphocytes through the SSC region of spleen was profoundly inhibited by mannan. Finally, direct evidence for adhesion between lymphocytes and SSC was obtained with spleen cell suspensions where clustering between Fl-mannan labeled SSC and lymphocytes was observed. Collectively, these data indicate that mannan (and PPME) inhibit splenic entry of lymphocytes by interacting with SSC, cell which play a critical role in the entry of lymphocytes into the spleen. Whether mannan-specific receptors on SSC directly mediate lymphocyte-SSC adhesion or play on indirect role in modifying lymphocyte migration requires further investigation.

Animals↗
PubMed1999

Albumin modified with mannose 6-phosphate: A potential carrier for selective delivery of antifibrotic drugs to rat and human hepatic stellate cells.

The hallmark of liver fibrosis is an increased extracellular matrix deposition, caused by an activation of hepatic stellate cells (HSC). Therefore, this cell type is an important target for pharmacotherapeutic intervention. Antifibrotic drugs are not efficiently taken up by HSC or may produce unwanted side-effects outside the liver. Cell-specific delivery can provide a solution to these problems, but a specific drug carrier for HSC has not been described until now. The mannose 6-phosphate/insulin-like growth factor II (M6P/IGF-II) receptor, which is expressed in particular upon HSC during fibrosis, may serve as a target-receptor for a potential carrier. The aim of the present study was to examine if human serum albumin (HSA) modified with mannose 6-phosphate (M6P) is taken up by HSC in fibrotic livers. A series of M6Px-modified albumins were synthetized: x = 2, 4, 10, and 28. Organ distribution studies were performed to determine total liver uptake. The hepatic uptake of M6Px-HSA increased with increasing M6P density. M6Px-HSA with a low degree of sugar loading (x = 2-10) remained in the plasma and accumulated for 9% +/- 0.5% or less in fibrotic rat livers. An increase in the molar ratio of M6P:HSA to 28:1 caused an increased liver accumulation to 59% +/- 9% of the administered dose. Furthermore, we determined quantitatively the in vivo intrahepatic distribution of M6Px-HSA using double-immunostaining techniques. An increased substitution of M6P was associated with an increased accumulation in HSC; 70% +/- 11% of the intrahepatic staining for M6P28-HSA was found in HSC. We also demonstrate that M6P-modified bovine serum albumin (BSA) accumulates in slices of normal and cirrhotic human livers. After incubation of this neoglycoprotein with human tissue, the protein is found in nonparenchymal liver cells. Because M6P-modified albumins are taken up by HSC in fibrotic livers, this neoglycoprotein can be applied as a selective drug carrier for HSC. This technology may create new opportunities for the pharmacological intervention of liver fibrosis.

Animals↗
PubMed1992

The desmoplastic response: induction of collagen synthesis by melanoma cells in vitro.

When cells from the human malignant melanoma cell line, UCT-Mel 7, were injected into athymic nude mice, tumours developed that were intensely infiltrated with fibrous tissue. In an attempt to reproduce this desmoplastic response in vitro, we co-cultured fibroblasts with UCT-Mel-7 cells, and observed a 2-fold increase in the rate of fibroblast collagen synthesis. This was associated with an increase in the amount of collagen mRNA present in co-cultured fibroblasts. The stimulation was both dose- and time-dependent, with maximal stimulation at a melanoma cell:fibroblast ratio of 1:1. Analysis of the kinetics of proline incorporation into collagen showed that co-culture affected the maximal rate of proline incorporation; no effect was observed on the concentration of proline required for 50% maximal collagen synthesis. The induction of fibroblast collagen synthesis showed an absolute requirement for close proximity between the fibroblasts and the melanoma cells. No soluble fibrogenic factor released by melanoma was detected.

Animals↗
PubMed1984

Antibody to mannose 6-phosphate specific receptor induces receptor deficiency in human fibroblasts.

Polyclonal antibodies to the mannose 6-phosphate specific receptor from human liver inhibited the endocytosis of lysosomal enzymes in fibroblasts by greater than 95% and enhanced 3-20-fold the secretion of precursors of lysosomal enzymes in these cells. Exposing fibroblasts for 4 h to antibody resulted in loss of greater than 90% of the membrane-bound receptors. If fibroblasts were treated with the antibody in the presence of CBZ-Phe-Ala-CHN2, an inhibitor of lysosomal cysteine proteinases, the receptor and smaller degradation products are recovered in dense lysosomes. In treated cells 18-58% of total receptor-related polypeptides were recovered in dense lysosomes. In control cells less than 4% of the receptor was found in the lysosomal fraction. We conclude from these results that normally the receptor is spared from lysosomal degradation. When tagged with antibody, however, the receptor is transported into lysosomes and degraded. The loss of intracellular receptors involved in segregation of newly synthesized lysosomal enzymes indicates an exchange between the former and the plasma membrane-bound receptors.

Animals↗
PubMed1984

A cycloheximide-resistant pool of receptors for asialoglycoproteins and mannose 6-phosphate residues in the Golgi complex of hepatocytes.

Following in vivo administration of cycloheximide (20 mg/kg body weight i.p.) protein synthesis was completely inhibited (99%) in rat liver. No newly synthesized asialoglycoprotein receptor (ASGP-R) could be detected by metabolic labeling. Fluorescence immunocytochemistry of several secretory proteins and plasma membrane proteins, including the receptors for polymeric IgA (IgA-R), demonstrated a rapid loss from the Golgi complex following cycloheximide administration. On the other hand, two membrane proteins, the receptors for ASGP-R and mannose 6-phosphate (MP-R), were not altered in their cellular localization including the Golgi. Using quantitative immunoelectron microscopy with colloidal gold, we found that 2 h and 4 h after cycloheximide administration, the densities of ASGP-R and MP-R in the membranes of the Golgi complex were unaltered compared with control liver. Similarly, there was no significant effect of cycloheximide on the receptor labeling in coated vesicles and compartment of uncoupling receptors and ligands (CURL). These observations are consistent with an involvement of the Golgi and CURL pools of the receptors in intracellular trafficking, endocytosis and receptor recycling.

Animals↗
PubMed1985

Internalization of blocking antibodies against mannose-6-phosphate specific receptors.

Antibodies against mannose-6-phosphate specific receptors inhibit the receptor-dependent endocytosis of exogenous lysosomal enzymes as well as the sorting of endogenous lysosomal enzymes. This inhibition was correlated with an apparent loss of the receptors. We report here that treatment of cells with the antibody results in the formation of receptor-antibody complexes that are not extracted by the procedure used for the solubilization of receptors prior to immunoprecipitation and detection of the receptor. The apparent loss of receptors is observed with both native antibody and the F(ab)2 fragments, but not with Fab fragments. In contrast the transport of lysosomal enzymes is inhibited by all three forms of the antibody. The inhibition is ascribed to masking by the antibody of the enzyme-binding site in the receptor. The inhibition of the sorting of endogenous lysosomal enzymes by antibodies added to the medium indicates that the mannose-6-phosphate specific receptors at the sorting site are in dynamic equilibrium with those at the cell surface. The receptor-antibody complexes formed at the cell surface appear to cycle between the cell surface and intracellular membranes. A fraction of the internalized antibodies dissociates from the receptors and is degraded after transfer into lysosomes. Complexing with Fab increases the concentration of the receptor in the lysosomes and decreases 2- to 3-fold the half-life of the receptor.

Antibodies↗
PubMed1985

Assembly of the mannose-6-phosphate receptor into reconstituted clathrin coats.

In ionic conditions in which clathrin coats are stable, the mannose-6-phosphate receptor associates with the 100-kd/50-kd coat complexes purified from bullock brain coated vesicles. These aggregates exist as striking spherical structures of 300-1000 A diameter. When clathrin is included in the assembly mixture, cages are formed which apparently encapsulate these aggregates, giving, in the absence of lipid, structures resembling full coated vesicles.

Animals↗
PubMed1987

Mr 46,000 mannose 6-phosphate specific receptor: its role in targeting of lysosomal enzymes.

Antibodies that block the ligand binding site of the cation-dependent mannose 6-phosphate specific receptor (Mr 46,000 MPR) were used to probe the function of the receptor in transport of lysosomal enzymes. Addition of the antibodies to the medium of Morris hepatoma 7777 cells, which express only the Mr 46,000 MPR, resulted in a decreased intracellular retention and increased secretion of newly synthesized lysosomal enzymes. In fibroblasts and HepG2 cells that express the cation-independent mannose 6-phosphate specific receptor (Mr 215,000 MPR) in addition to the Mr 46,000 MPR, antibodies against the Mr 46,000 MPR inhibited the intracellular retention of newly synthesized lysosomal enzymes only when added to the medium together with antibodies against the Mr 215,000 MPR. Morris hepatoma (M.H.) 7777 did not endocytose lysosomal enzymes, while U937 monocytes, which express both types of MPR, internalized lysosomal enzymes. The uptake was inhibited by antibodies against the Mr 215,000 MPR, but not by antibodies against the Mr 46,000 MPR. These observations suggest that Mr 46,000 MPR mediates transport of endogenous but not endocytosis of exogenous lysosomal enzymes. Internalization of receptor antibodies indicated that the failure to mediate endocytosis of lysosomal enzymes is due to an inability of surface Mr 46,000 MPR to bind ligands rather than its exclusion from the plasma membrane or from internalization.

Animals↗
PubMed1987

Thyroglobulin, the major and obligatory exportable protein of thyroid follicle cells, carries the lysosomal recognition marker mannose-6-phosphate.

Thyroglobulin (TG), the major exportable protein of thyroid follicle cells, is conveyed to lysosomes on a complex secretion, storage and recapture pathway by as yet unknown transport mechanisms. This report establishes that the dimeric porcine TG-molecule carries an average of six phosphate residues. Endoglycosidase digestion showed that two phosphate residues are bound to the high-mannose carbohydrate side chains (CHO), while two others are linked to the complex CHO. These four residues are also sensitive to alkaline phosphatase treatment, indicating their terminal linkage. Immunoprecipitation analyses showed that TG obtained from microsomal fractions is already phosphorylated. Most important, an enzymatic assay applied to hydrolysates of TG established that the two phosphate residues at the high mannose CHO are present as mannose-6-phosphate (M-6-P). Alkaline phosphatase treatment of biosynthetically radiophosphorylated CHO followed by hydrolysis and t.l.c. indicated that M-6-P is present at least in part in phosphomonoester linkage. Furthermore, porcine TG binds specifically to the M-6-P receptor of Chinese hamster ovary cells. It is concluded that the M-6-P residues of TG are exposed and able to operate as a ligand for the M-6-P receptor. It is unknown why the lysosomal recognition-marker M-6-P does not convey TG directly on an intracellular route to lysosomes. We propose that for the secretion of newly synthesized TG into the follicle lumen an additional export signal dominating over the M-6-P recognition-marker is required.

Animals↗
PubMed1988

Receptors compete for adaptors found in plasma membrane coated pits.

An affinity matrix of LDL receptor cytoplasmic tails binds the HA-II 100/50/16 kd complexes found in plasma membrane coated pits. Other receptors (or their cytoplasmic domains), which are localized in coated pits during endocytosis, inhibit this binding. This includes an 8 residue peptide containing tyrosine, corresponding to the cytoplasmic portion of a mutant influenza haemagglutinin. In contrast, the equivalent peptide lacking tyrosine (like the tail of the native haemagglutinin, a protein excluded from coated pits) does not compete. These results imply that the HA-II complex has a recognition site for a common signal, probably involving a tyrosine residue, carried by the LDL receptor and competing receptors also found in plasma membrane coated pits. The HA-II complex therefore fulfils the role of an 'adaptor', the name proposed for the structural units which mediate the binding of clathrin to receptors in coated vesicles. Another related complex, the HA-I adaptor, which is restricted to Golgi coated pits, probably does not recognize the 'tyrosine signal' on the LDL receptor tail. The HA-I adaptor is likely to contain a recognition site for a different signal carried by receptors, e.g. the mannose-6-phosphate receptor, which are found in Golgi coated pits.

Coated Pits, Cell-Membrane↗
PubMed1989

Regulation of the mannose 6-phosphate/IGF II receptor expression at the cell surface by mannose 6-phosphate, insulin like growth factors and epidermal growth factor.

Mannose 6-phosphate, insulin like growth factors I and II (IGF I, IGF II), insulin and epidermal growth factor (EGF) induce a 1.5- to 2-fold increase of mannose 6-phosphate binding sites at the cell surface of human skin fibroblasts. The increase is completed within 10-15 min, is dose and temperature dependent, reversible and transient even in the presence of the effectors. It is due to a redistribution of mannose 6-phosphate/IGF II receptors from internal membranes to the cell surface, while the affinity of the receptors is not affected. Combinations of mannose 6-phosphate with IGF I, IGF II or EGF stimulate the redistribution of the receptor to the cell surface in an additive manner, while combinations of the growth factors result in a non-additive stimulation of redistribution. The redistribution is not dependent on extracellular calcium and appears also to be independent of changes of free intracellular calcium. Pre-treatment of fibroblasts with cholera toxin or pertussis toxin increases the number of cell surface receptors 2- and 1.5-fold, respectively. Neither of the toxins affects the redistribution of mannose 6-phosphate/IGF II receptors induced by the growth factors, while both toxins abolish the receptor redistribution induced by mannose 6-phosphate. These results suggest a multiple regulation of the cell surface expression of mannose 6-phosphate/IGF II receptors by Gs- and Gi-like proteins sensitive to cholera toxin and pertussis toxin and by stimulation of mannose 6-phosphate/IGF II, IGF I and EGF receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium↗
PubMed1990

Mannose 6-phosphate receptor dependent secretion of lysosomal enzymes.

BHK and mouse L cells transfected with the cDNA for the human 46 kd mannose 6-phosphate receptor (MPR 46) secrete excessive amounts of newly synthesized mannose 6-phosphate containing polypeptides. The secretion is dependent on the amount, the recycling and the affinity for ligands of MPR 46. Incubation of transfected cells with antibodies blocking the binding site of MPR 46 reduces the secretion, and cotransfection with the cDNA for the human 300 kd mannose 6-phosphate (MPR 300) restores it to normal values. These results indicate that the two mannose 6-phosphate receptors compete for binding of newly synthesized ligands. In contrast to ligands bound to MPR 300, those bound to the MPR 46 are transported to and released at a site, e.g. early endosomes or plasma membrane, from where they can exit into the medium. Since antibodies blocking the binding site of MPR 46 reduce secretion also in non-transfected BHK and mouse L cells, at least part of the basal secretion of M6P-containing polypeptides is mediated by the endogenous MPR 46.

Animals↗
PubMed1991

Transplanted LDL and mannose-6-phosphate receptor internalization signals promote high-efficiency endocytosis of the transferrin receptor.

The internalization signals of several constitutively recycling receptors have recently been identified as regions of four or six amino acids that include an aromatic residue, usually tyrosine. Here, we show that transplanted signals from the low density lipoprotein receptor (LDLR) and cation-independent mannose-6-phosphate receptor (Man-6-PR) promote rapid internalization of the transferrin receptor (TR), directly establishing that recognition signals are interchangeable, self-determined structural motifs and that signals from type I membrane proteins are active in a type II receptor. We also show that the chemical and spatial patterns of critical residues in both four- and six-residue internalization motifs are consistent with a tight turn structure. A six-residue LDLR signal is needed for activity in TR, suggesting that an amino-terminal aromatic side chain is obligatory. In contrast, the carboxy-terminal aromatic side chain in the TR signal can be replaced by a large hydrophobic residue. Thus, internalization signals apparently require an aromatic amino-terminal residue and either an aromatic or large hydrophobic carboxy-terminal residue rather than a conserved tyrosine per se. Consistent with this conclusion, predicted internalization signals from the poly-Ig receptor, YSAF, and asialoglycoprotein receptor (ASGPR) subunit H1, YQDL, also promote internalization of TR.

Amino Acid Sequence↗
PubMed1992

Human serum amyloid P is a multispecific adhesive protein whose ligands include 6-phosphorylated mannose and the 3-sulphated saccharides galactose, N-acetylgalactosamine and glucuronic acid.

Carbohydrate recognition by amyloid P component from human serum has been investigated by binding experiments using several glycosaminoglycans, polysaccharides and a series of structurally defined neoglycolipids and natural glycolipids. Two novel classes of carbohydrate ligands have been identified. The first is 6-phosphorylated mannose as found on lysosomal hydrolases, and the second is the 3-sulphated saccharides galactose, N-acetyl-galactosamine and glucuronic acid as found on sulphatide and other acidic glycolipids that occur in neural or kidney tissues or on subpopulations of lymphocytes. Binding to mannose-6-phosphate containing molecules and inhibition of binding by free mannose-6-phosphate and fructose-1-phosphate are features shared with mannose-6-phosphate receptors involved in trafficking of lysosomal enzymes. However, only amyloid P binding is inhibited by galactose-6-phosphate, mannose-1-phosphate and glucose-6-phosphate. These findings strengthen the possibility that amyloid P protein has a central role in amyloidogenic processes: first in formation of focal concentrations of lysosomal enzymes including proteases that generate fibril-forming peptides from amyloidogenic proteins, and second in formation of multicomponent complexes that include sulphoglycolipids as well as glycosaminoglycans. The evidence that binding to all of the acidic ligands involves the same polypeptide domain on amyloid P protein, and inhibition data using diffusible, phosphorylated monosaccharides, is potentially important leads to novel drug designs aimed at preventing or even reversing amyloid deposition processes without interference with essential lysosomal trafficking pathways.

Acetylgalactosamine↗
PubMed1994

Differential sorting of lysosomal enzymes in mannose 6-phosphate receptor-deficient fibroblasts.

In higher eukaryotes, the transport of soluble lysosomal enzymes involves the recognition of their mannose 6-phosphate signal by two receptors: the cation-independent mannose 6-phosphate/insulin-like growth factor II receptor (CI-MPR) and the cation-dependent mannose 6-phosphate receptor (CD-MPR). It is not known why these two different proteins are present in most cell types. To investigate their relative function in lysosomal enzyme targeting, we created cell lines that lack either or both MPRs. This was accomplished by mating CD-MPR-deficient mice with Thp mice that carry a CI-MPR deleted allele. Fibroblasts prepared from embryos that lack the two receptors exhibit a massive missorting of multiple lysosomal enzymes and accumulate undigested material in their endocytic compartments. Fibroblasts that lack the CI-MPR, like those lacking the CD-MPR, exhibit a milder phenotype and are only partially impaired in sorting. This demonstrates that both receptors are required for efficient intracellular targeting of lysosomal enzymes. More importantly, comparison of the phosphorylated proteins secreted by the different cell types indicates that the two receptors may interact in vivo with different subgroups of hydrolases. This observation may provide a rational explanation for the existence of two distinct mannose 6-phosphate binding proteins in mammalian cells.

Animals↗
PubMed1995

Glycosylinositol-phosphoceramide in the free-living protozoan Paramecium primaurelia: modification of core glycans by mannosyl phosphate.

Glycolipids synthesized in a cell-free system prepared from the free-living protozoan Paramecium primaurelia and labelled with [3H]mannose and [3H]glucosamine using GDP-[3H]mannose and UDP-[3H]N-acetyl glucosamine, respectively, were identified and structurally characterized as glycosylinositol-phosphoceramides (GIP-ceramides). The ceramide-based lipid was also found in the GIP membrane anchor of the G surface antigen of P.primaurelia, strain 156. Using a combination of in vitro labelling with GDP-[3H]mannose and in vivo labelling with 33P, we found that the core glycans of the P.primaurelia GIP-ceramides were substituted with an acid-labile modification identified as mannosyl phosphate. The modification of the glycosylinositol-phospholipid core glycan by mannosyl phosphate has not been described to date in other organisms. The biosynthesis of GIP-ceramide intermediates in P.primaurelia was studied by a pulse-chase analysis. Their structural characterization is reported. We propose the following structure for the putative GIP-ceramide membrane anchor precursor of P.primaurelia surface proteins: ethanolamine phosphate-6Man-alpha 1-2Man-alpha 1-6Man-(mannosyl phosphate)-alpha 1-4glucosamine-inositol-phosphoceramide.

Animals↗