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At least 1,153 records · Page 64Linked to original sources
PubMed1997

The aberrant cell walls of boron-deficient bean root nodules have no covalently bound hydroxyproline-/proline-rich proteins.

B-deficient bean (Phaseolus vulgaris L.) nodules examined by light microscopy showed dramatic anatomical changes, mainly in the parenchyma region. Western analysis of total nodule extracts examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that one 116-kD polypeptide was recognized by antibodies raised against hydroxyproline-rich glycoproteins (HRGPs) from the soybean (Glycine max) seed coat. A protein with a comparable molecular mass of 116 kD was purified from the cell walls of soybean root nodules. The amino acid composition of this protein is similar to the early nodulin (ENOD2) gene. Immunoprecipitation of the soybean ENOD2 in vitro translation product showed that the soybean seed coat anti-HRGP antibodies recognized this early nodulin. Furthermore, we used these antibodies to localize the ENOD2 homolog in bean nodules. Immunocytochemistry revealed that in B-deficient nodules ENOD2 was absent in the walls of the nodule parenchyma. The absence of ENOD2 in B-deficient nodules was corroborated by performing hydroxyproline assays. Northern analysis showed that ENOD2 mRNA is present in B-deficient nodules; therefore, the accumulation of ENOD2 is not affected by B deficiency, but its assembly into the cell wall is. B-deficient nodules fix much less N2 than control nodules, probably because the nodule parenchyma is no longer an effective O2 barrier.

Boron↗
PubMed2002

Differential effects of cadmium on proteoglycan synthesis of arterial smooth muscle cells: increase in small dermatan sulfate proteoglycans, biglycan and decorin, in the extracellular matrix at low cell density.

Proteoglycans (PGs), especially chondroitin/dermatan sulfate proteoglycans (CS/DSPGs), accumulate and their composition variously changes in atherosclerotic vascular walls. Since cadmium causes atherosclerosis in experimental animals, PGs synthesized by cultured vascular smooth muscle cells after exposure to cadmium were characterized in the present study. Sparse and dense cultures of the cells were metabolically labeled with [35S]sulfate for 24 h in the presence of cadmium chloride at noncytotoxic levels (0.2 microM or less). The incorporation of [35S]sulfate into glycosaminoglycans was determined by the cetylpyridinium chloride precipitation method. The labeled PGs were characterized by DEAE-Sephacel ion exchange chromatography and Sepharose CL-4B molecular sieve chromatography. The M(r) and the glycosaminoglycan composition of small CS/DSPGs were analyzed by SDS-polyacrylamide gel electrophoresis and Sepharose CL-6B chromatography, respectively, before and after digestion with chondroitin ABC lyase or papain. The core proteins were identified by Western blot analysis. These experiments indicate that cadmium differentially acts on the PG synthesis when vascular smooth muscle cell density is low. Specifically, cadmium increased the accumulation of small CS/DSPGs identified as biglycan and decorin in the cell layer of sparse cells. However, the hydrodynamic size and the length of chondroitin/dermatan sulfate chains in the PGs were unaffected by cadmium. On the other hand, cadmium decreased other cell layer-associated PGs that were separated from biglycan and decorin by DEAE-Sephacel chromatography in the sparse cells; as the result, whole glycosaminoglycans were decreased in both the cell layer and the conditioned medium. It is therefore concluded that cadmium may change the composition of PGs in atherosclerotic plaques through induction of biglycan and decorin synthesis and inhibition of other PG synthesis in vascular smooth muscle cells.

Animals↗
PubMed1994

Compositional analysis of the oligosaccharide units of xyloglucans from suspension-cultured poplar cells.

Xyloglucan which was isolated from the walls of suspension-cultured poplar cells showed an average mol wt of 45,000; the extracellular xyloglucan is 25,000 mol wt. Compositional analysis of the oligosaccharide units with Streptomyces endo-1,4-beta-glucanase indicated that the polysaccharides were mainly constructed of four kinds of oligosaccharide repeating units, XLFG, XXFG, XXLG, and XXXG. Poplar xyloglucans contain these four units distributed at random, but primarily at the same ratio among their molecules.

Carbohydrate Sequence↗
PubMed1991

Isolation and characterization of Saccharomyces cerevisiae mutants resistant to aculeacin A.

Aculeacin A is a lipopeptide that inhibits beta-glucan synthesis in yeasts. A number of Saccharomyces cerevisiae mutants resistant to this antibiotic were isolated, and four loci (ACR1, ACR2, ACR3, and ACR4) whose products are involved in the sensitivity to aculeacin A of yeast cells were defined. Mutants containing mutations in the four loci were also resistant to echinocandin B, another member of this lipopeptide family of antibiotics. In contrast, acr1, acr3, and acr4 mutants were resistant to papulacandin B (an antibiotic containing a disaccharide linked to two fatty acid chains that also inhibits beta-glucan synthesis), but acr2 mutants were susceptible to this antibiotic. This result defines common and specific steps in the entry and action of aculeacin A and papulacandin B. The analysis of double mutants revealed an epistatic effect of the acr2 mutation on the other three mutations. Cell walls of the four different mutants did not show significant alterations in composition with respect to the parental strain, and in vitro glucan synthase activity was also unaffected. However, cell surface hydrophobicity in three of the mutants was considerably decreased with respect to the parental strain.

Aminoglycosides↗
PubMed2001

Rapid deposition of extensin during the elicitation of grapevine callus cultures is specifically catalyzed by a 40-kilodalton peroxidase.

Elicitation or peroxide stimulation of grape (Vitis vinifera L. cv Touriga) vine callus cultures results in the rapid and selective in situ insolubilization of an abundant and ionically bound cell wall protein-denominated GvP1. Surface-enhanced laser desorption/ionization/time of flight-mass spectrometry analysis, the amino acid composition, and the N-terminal sequence of purified GvP1 identified it as an 89.9-kD extensin. Analysis of cell walls following the in situ insolubilization of GvP1 indicates large and specific increases in the major amino acids of GvP1 as compared with the amino acids present in salt-eluted cell walls. We calculate that following deposition, covalently bound GvP1 contributes up to 4% to 5% of the cell wall dry weight. The deposition of GvP1 in situ requires peroxide and endogenous peroxidase activity. Isoelectric focusing of saline eluates of callus revealed only a few basic peroxidases that were all isolated or purified to electrophoretic homogeneity. In vitro and in situ assays of extensin cross-linking activity using GvP1 and peroxidases showed that a 40-kD peroxidase cross-linked GvP1 within minutes, whereas other grapevine peroxidases had no significant activity with GvP1. Internal peptide sequences indicated this extensin peroxidase (EP) is a member of the class III peroxidases. We conclude that we have identified and purified an EP from grapevine callus that is responsible for the catalysis of GvP1 deposition in situ during elicitation. Our results suggest that GvP1 and this EP play an important combined role in grapevine cell wall defense.

Adaptation, Physiological↗
PubMed1995

Cellular, biological, and physicochemical basis for the hard-to-cook defect in legume seeds.

This review integrates current knowledge on the hard-to-cook (HTC) defect in legume seeds, with emphasis on the cellular and biological changes during storage and soaking, and the physicochemical changes during heating. Several postulated mechanisms, including the pectin-cation-phytate model, cell lignification, pectin beta-eliminative degradation, and protein denaturation in relation to starch gelatinization, are discussed in the context of current evidence. Subsequently, a developmental model of legume hardening is presented. It is held that the HTC defect develops during aging and soaking and is exhibited through cooking. During the process, there are many events involved. Free radical formation, lipid peroxidation, acid formation, membrane deterioration, protein denaturation, and leakage are events associated with aging and soaking, whereas pectin decomposition and solubilization, protein coagulation, and starch gelatinization are events that occur during cooking. Cooked HTC seeds are characterized by limited cell separation and restricted starch gelatinization. These defective features result from a restriction in pectin decomposition and solubilization as well as the protein coagulation that prevails over starch gelatinization during heating. This multichannel mechanism points to the direct involvement of two amphoteric colloids, cell wall pectin and storage protein, both of which are sensitive to pH and/or ion composition. The model also indicates the indirect involvement of cell membranes and starch granules. Except for events that occur during aging and soaking, it is likely that heat-related textural problems in other plant tissues may proceed via a mechanism similar to legume hardening.

Cell Wall↗
PubMed1983

Occurrence of antigenic (species-specific?) partially 3-O-methylated heteromannans in cell wall and soluble cellular (nonwall) components of Coccidioides immitis mycelia.

Skin test-active, phenol-soluble, water-soluble (PSWS) extracts of Coccidioides immitis whole, defatted mycelia were compared with skin test-active, alkali-soluble, water-soluble (ASWS) extracts of mycelial cell walls. Both PSWS and ASWS extracts contained partially 3-O-methylated mannan. Composition analysis of both PSWS and ASWS extracts indicated mannose and glucose as major components, whereas 3-O-methylmannose and galactose were minor constituents. These heteromannans and glucans could be obtained from cell walls by extraction with either mild acid or alkali, but not with aqueous phenol. We therefore conclude that the PSWS extracts which were obtainable from whole mycelia but not from cell walls represent cellular (i.e., periplasmic, membrane associated, or cytoplasmic), nonwall polymers. Both PSWS and ASWS mycelial extracts and their gel filtration fractions reacted with rabbit antispherule serum, but with little cross-reactivity. However, alkali treatment of higher-molecular-weight PSWS extract polymers yielded products that cross-reacted with serological identity with low-molecular-weight components of ASWS extracts of mycelial walls, indicating that cell walls and cellular polymers share antigenic determinants. Finally, gel filtration of PSWS extracts on Sephacryl S-200 and Sepharose CL 4B yielded fractions that reacted with serological identity with one or more components of mycelial cytosol, mycelial culture filtrate and autolysate coccidioidins, and spherulin.

Animals↗
PubMed2000

Differential localization of arabinan and galactan side chains of rhamnogalacturonan 1 in cambial derivatives.

The development of pectin structural features during the differentiation of cambial derivatives was investigated in aspen (Populus tremula L. x P. tremuloides Michx.) using biochemical and immunocytochemical methods. Comparisons were also made between active and resting tissues. Active tissues, in particular cambial cells and phloem derivatives, were characterized by a high pectin content. Use of antibodies raised against arabinan side chains of rhamnogalacturonan 1 (LM6), as well as biochemical analysis, revealed an obvious decrease from the cortex to the differentiating xylem. Galactan side chains, detected with LM5 antibodies, were present mainly in the cambial zone and enlarging xylem cells. In contrast, they were totally absent from sieve-tube cell walls. Image analysis of LM5 immunogold labelling in the cambial zone showed a clustered distribution of galactan epitopes in the radial walls, a distribution which might result from the association of two different periodic processes, namely the exocytosis of galactan and wall expansion. Cessation of cambial activity was characterized by cell wall thickening accompanied by a sharp decrease in the relative amount of pectin and a lowering of the degree of methylesterification. The data provide evidence that the walls of phloem and xylem cells differ in their pectin composition even at a very early stage of commitment. These differences offer useful tools for identifying the initial cells among their immediate neighbours.

Cell Wall↗
PubMed2005

Xyloglucan is recognized by carbohydrate-binding modules that interact with beta-glucan chains.

Enzyme systems that attack the plant cell wall contain noncatalytic carbohydrate-binding modules (CBMs) that mediate attachment to this composite structure and play a pivotal role in maximizing the hydrolytic process. Although xyloglucan, which includes a backbone of beta-1,4-glucan decorated primarily with xylose residues, is a key component of the plant cell wall, CBMs that bind to this polymer have not been identified. Here we showed that the C-terminal domain of the modular Clostridium thermocellum enzyme CtCel9D-Cel44A (formerly known as CelJ) comprises a novel CBM (designated CBM44) that binds with equal affinity to cellulose and xyloglucan. We also showed that accommodation of xyloglucan side chains is a general feature of CBMs that bind to single cellulose chains. The crystal structures of CBM44 and the other CBM (CBM30) in CtCel9D-Cel44A display a beta-sandwich fold. The concave face of both CBMs contains a hydrophobic platform comprising three tryptophan residues that can accommodate up to five glucose residues. The orientation of these aromatic residues is such that the bound ligand would adopt the twisted conformation displayed by cello-oligosaccharides in solution. Mutagenesis studies confirmed that the hydrophobic platform located on the concave face of both CBMs mediates ligand recognition. In contrast to other CBMs that bind to single polysaccharide chains, the polar residues in the binding cleft of CBM44 play only a minor role in ligand recognition. The mechanism by which these proteins are able to recognize linear and decorated beta-1,4-glucans is discussed based on the structures of CBM44 and the other CBMs that bind single cellulose chains.

Amino Acid Motifs↗
PubMed1996

Oxidized low density lipoproteins in atherogenesis: role of dietary modification.

The development of atherosclerosis is a complex and multistep process. There are many determinants in the pathogenesis of this condition, with different factors presumably playing key roles at different times in the evolution of the atherosclerotic plaque. It has been suggested that oxidation of low density lipoproteins (LDL) by cells in the artery wall leads to a proatherogenic particle that may help initiate early lesion formation. For this reason, understanding the determinants of LDL susceptibility to oxidation is essential for developing therapeutic strategies to inhibit this process. Oxidation of LDL begins with the abstraction of hydrogen from polyunsaturated fatty acids; thus, LDL fatty acid composition undoubtedly contributes to the process of LDL oxidation. Since dietary fatty acids influence the fatty acid composition of LDL and cell membranes, the amount and type of fat in the diet may effect susceptibility of LDL and cells to oxidative damage. Additionally, since cell membrane fatty acid composition also influences cellular formation of reactive oxygen species, dietary fatty acids may help determine the prooxidant activity of artery wall cells. Both cells and lipoproteins contain a variety of antioxidants that provide protection against oxidative stress. A major source of these antioxidants is the diet. Enrichment of the diet with foods high in such antioxidants as vitamin E, beta-carotene, or vitamin C, or supplementation of the diet with antioxidant vitamins, may inhibit oxidation and the process of atherosclerosis.

Arteriosclerosis↗
PubMed2000

Apoptosis in inflammatory-fibroproliferative disorders of the vessel wall.

Apoptotic cell death is a hallmark of inflammatory-fibroproliferative disorders of the vessel wall. Here, we review what is currently known about cell death within atherosclerotic and restenotic lesions. We also examine evidence suggesting that inflammatory cells contribute to the regulation of cell turnover within these lesions, and discuss the molecules expressed by vascular cells that modulate these processes. In toto, these studies suggest that apoptosis is prevalent in vascular lesions, controlling the viability of both inflammatory and vascular cells, and thus determining the cellular composition of the vessel wall.

Apoptosis↗
PubMed2006

[Degradation of cell wall polysaccharides during postharvest fruit ripening and softening of different apple varieties].

The cell wall material (CWM) and eight cell wall polysaccharides fractions were extracted from 'Fuji' and 'Kinsei' apples during storage at different time (0 and 42 days). The sugar composition characteristics of each fraction were determined by gas chromatography. The results showed that, during storages, the firmness of 'Kinsei' apples decreased significantly, and a significant peak of ethylene production was shown after 10 d storage, but only a little ethylene was produced in 'Fuji' apples, which had a better storability. Compare to other cell wall polysaccharide fractions, in Na(2)CO(3)-soluble pectic fractions of apple fruit, there were abundant rhamnogalacturonan I (RG-I), which branched highly in side chains due to the compositions of arabinans, galactans, arabinogalactans etc. As for cell wall polysaccharides, in 'Kinsei' apples, the decrease of pectic fractions was shown most significantly in Na(2)CO(3)-1 fraction, which was associated with a significant degradation of arabinosyl and galactosyl residues on the side chains. Further more, higher molecular mass in Na(2)CO(3)-1 pectic polysaccharides degraded and turned into ones with smaller molecular mass. From these results, the degradation of side chains in Na(2)CO(3)-1 pectic polysaccharides under the activity of enzyme was considered one of the most significant factors of apple fruit softening through modifying the network of cell wall polysaccharides.

Carbonates↗
PubMed1972

Comparative electrophoretic and amino acid analyses of isolated membranes from Streptococcus pyogenes and stabilized L-form.

Major quantitative, but not qualitative, differences in the various species of proteins in purified membranes from Streptococcus pyogenes and its stabilized L-form have been demonstrated by acidic and alkaline disc gel electrophoresis with and without urea. The fact that no significant differences in the amino acid content or composition between these two membranes could be demonstrated emphasizes that these results are probably due to changes in the relative amounts of the various species of proteins in this subcellular component. The possibility of these protein changes in the L-form membrane being related to its inability to synthesize a rigid cell wall is discussed. Finally, phage-associated lysin, routinely used for removal of the group A streptococcal cell wall, does not appear to affect the protein profile or amino acid composition of the membrane either metabolically or nonmetabolically.

Amino Acids↗
PubMed1996

Tunica media remodeling in mesenteric arteries of hypertensive rats.

BACKGROUND: The tunica media of the vascular wall is a composite material comprised of smooth muscle cells and fibrous and nonfibrous matrix proteins. METHODS: Using morphometric techniques, this study quantifies the cell and matrix composition of normotensive (Wistar-Kyoto) and spontaneously hypertensive rat mesenteric arteries. RESULTS: The data show that the superior mesenteric artery (SMA) and small mesenteric arteries are different in matrix composition, cell-to-matrix ratio, and cellular dense body content. Compared with normotensive arteries, hypertensive arteries have less basement membrane but more collagen and extracellular matrix ground substance. SMA from hypertensive rats has about 30% less elastin than does normotensive artery. In contrast, the elastin content of small arteries of both strains was about the same and was less than 4% of the matrix area. Except in hypertensive SMA, membrane dense bodies occupy 7-10% of the cell area and more than 10 times the area occupied by cytoplasmic dense bodies. In contrast, cells from hypertensive SMA have about half the membrane dense body area of the normotensive cells. A decreased proportion of dense bodies in the hypertensive SMA is consistent with the "partial detachment" of these cells from the matrix. CONCLUSIONS: These results are consistent with both cellular and matrix "remodeling" in diseased vessels in response to continuous, long-term elevated blood pressure.

Animals↗
PubMed1996

Structure of the phosphopeptidomannans from flocculent and non-flocculent yeast Kluyveromyces lactis.

After extraction from whole cells, and purification by gel filtration, the chemical composition and molecular mass estimation of the cell-wall phosphopeptidomannan (PPM) showed no significant difference respectively between flocculent, weakly, very weakly and non-flocculent Kluyveromyces lactis yeast strains. However, when PPMs were tested as ligands of a lectin, extracted from the flocculent strain, the PPM isolated from the flocculent and weakly flocculent strain were recognized to a higher degree than those isolated from the non and very weakly flocculent strains. Acetolysis of PPM extracted from the four strains produced five oligosaccharide fractions corresponding to mono-, di-, tri-, penta-and hexa-saccharides. The flocculent strain was characterised by a high content of di-and penta-saccharides. The 1H NMR analysis of the oligosaccharides demonstrated that the flocculent strain contained equivalent levels of the two mannobioses: Man(alpha 1-->2)Man and Man(alpha 1-->3)Man and of the two mannotrioses Man(alpha 1-->2)Man(alpha 1-->2)Man and Man(alpha 1-->3)Man(alpha 1-->2)Man. In contrast, the non-flocculent and the very weakly flocculent strains contained a single type of mannobiose Man(alpha 1-->2)Man and one type of mannotriose Man(alpha 1-->2)Man(alpha 1-->2)Man.

Acetylglucosamine↗
PubMed1995

Conservation and variability in Archaea: protein antigens with tandem repeats encoded by a cluster of genes with common motifs in Methanosarcina mazei S-6.

Three open reading frames, orf492, orf375 and orf783, were identified in a 5.9-kb DNA fragment from the genome of Methanosarcina mazei S-6 that code for proteins recognized by antibodies against cell-surface antigens. The deduced amino-acid (aa) sequences of orfs492 and 375, i.e., ORF492 and ORF375, contain seven and four copies of an approx. 42-aa repeat, respectively. The aa sequence of ORF783 contains nine copies of an approx. 85-aa repeat, one of which is also present once in each of the first two ORFs. The organization of the repeats is similar to that of some Gram+ cell-wall-associated proteins. Comparative analyses of aa sequences, compositions and hydropathy profiles of the archaeal ORFs showed similarity with surface (S-) layer and outer-membrane proteins of Bacteria and Archaea.

Amino Acid Sequence↗