The formation of a stable complex between dissociated proteoglycan and hyaluronic acid in the absence of a link protein.
Ontology highlight
ABSTRACT:
SUBMITTER: Swann DA
PROVIDER: S-EPMC1163881 | biostudies-other | 1976 Aug
REPOSITORIES: biostudies-other
Similar Datasets
Project description:An electric field causes partial alignment of macromolecules in a dilute solution. The accompanying changes in the solution birefringence offer a sensitive and quick means of monitoring the rates of particle orientation and hence the size of the solute molecules. Such measurements are reported for dilute solutions of proteoglycans in the absence and presence of added hyaluronic acid. The proteoglycan molecules are shown to be some 580 nm long. In the presence of hyaluronic acid they form aggregates that appear to be consistent with the model previously proposed in which the proteoglycans attach radially to the extended hyaluronic acid chain. The electric-birefringence relaxation rates indicate aggregates of similar length to that of the extended hyaluronic acid chain, with the proteoglycans spaced on average at 29nm intervals. A proteoglycan sample the cystine residues of which had been reduced and alkylated showed no evidence of aggregation with hyaluronic acid up to the concentrations of the acid corresponding to 1% of the total uronic acid content. The electric-birefringence method is shown to have a large potential in the study of associating polysaccharide solutions.
| S-EPMC1185767 | biostudies-other
Project description:1. Dissociation of purified proteoglycan aggregates was shown to release an interacting component of buoyant density higher than that of the glycoprotein-link fraction of Hascall & Sajdera (1969). 2. This component, which produced an increase in hydrodynamic size of proteoglycans on gel chromatography, was isolated by ECTEOLA-cellulose ion-exchange chromatography and identified as hyaluronic acid. 3. The effect of pH of extraction showed that the proportion of proteoglycan aggregates isolated from cartilage was greatest at pH4.5. 4. The proportion of proteoglycans able to interact with hyaluronic acid decreased when extracted above or below pH4.5, whereas the amount of hyaluronic acid extracted appeared constant from pH3.0 to 8.5. 5. Sequential extraction of cartilage with 0.15m-NaCl at neutral pH followed by 4m-guanidinium chloride at pH4.5 was shown to yield predominantly non-aggregated and aggregated proteoglycans respectively. 6. Most of the hyaluronic acid in cartilage, representing about 0.7% of the total uronic acid, was associated with proteoglycan aggregates. 7. The non-aggregated proteoglycans were unable to interact with hyaluronic acid and were of smaller size, lower protein content and lower keratan sulphate content than the disaggregated proteoglycans. Together with differences in amino acid composition this suggested that each type of proteoglycan contained different protein cores.
| S-EPMC1166321 | biostudies-other
Project description:BackgroundLinks in complex networks commonly represent specific ties between pairs of nodes, such as protein-protein interactions in biological networks or friendships in social networks. However, understanding the mechanism of link formation in complex networks is a long standing challenge for network analysis and data mining.Methodology/principal findingsLinks in complex networks have a tendency to cluster locally and form so-called communities. This widely existed phenomenon reflects some underlying mechanism of link formation. To study the correlations between community structure and link formation, we present a general computational framework including a theory for network partitioning and link probability estimation. Our approach enables us to accurately identify missing links in partially observed networks in an efficient way. The links having high connection likelihoods in the communities reveal that links are formed preferentially to create cliques and accordingly promote the clustering level of the communities. The experimental results verify that such a mechanism can be well captured by our approach.Conclusions/significanceOur findings provide a new insight into understanding how links are created in the communities. The computational framework opens a wide range of possibilities to develop new approaches and applications, such as community detection and missing link prediction.
| S-EPMC3765235 | biostudies-literature
Project description:Cartilage proteoglycan aggregate formation was studied by zonal rate centrifugation in sucrose gradients. Proteoglycan aggregates, monomers and proteins could be resolved. It was shown that the optimal proportion of hyaluronic acid for proteoglycan aggregate formation was about 1% of proteoglycan dry weight. The reaggregation of dissociated proteoglycan aggregate A1 fraction was markedly concentration-dependent and even at 9 mg/ml only about 90% of the aggregates were reformed. The lowest proportion of link protein required for maximal formation of link-stabilized proteoglycan aggregates was 1.5% of proteoglycan dry weight. It was separately shown that link protein co-sedimented with the proteoglycan monomer. By competition with isolated hyaluronic acid-binding-region fragments, a proportion of the link proteins was removed from the proteoglycan monomers, indicating that the link protein binds to the hyaluronic acid-binding region of the proteoglycan monomer.
| S-EPMC1163179 | biostudies-other
Project description:OBJECTIVE:To study the correlation between hyaluronic acid (HA), hyaluronic acid synthase (HAS) and human renal clear cell carcinoma (RCCC). METHODS:The expression of three HAS isoforms' gene and HA in 93 RCCC tissues, 27 nephridial tissues by the side of RCCC from two hospitals were measured with Real-Time RT-PCR?Western Blot and immunohistochemical methods and analyzed. RESULTS:All RCCC and adjacent normal tissues expressed three HASs' mRNA & protein; at the mRNA level, both RCCC and adjacent normal tissues, expressed more HAS3 than HAS1 or HAS2, their differences were statistically significant (all P values <0.05); but, at the protein level, all HAS isoforms presented the equivalent expression. Compared with the adjacent non-neoplastic kidney tissues, the expression of all HAS isoforms' mRNA in RCCC tissues were increased evidently and their differences were significant (all P values <0.0001); but at the protein level, only the expression of HAS3 increased evidently (P=0.022). In all adjacent normal tissues, more than 80% renal tubular cells strongly expressed HA, however, only the minority RCCC cases (16/93) presented weakly positive HA staining in few cancer nests (5%-30%), the difference were significant (P<0.0001). In RCCC tissues subgrouped according to clinical stage, pathological grade, lymphatic metastasis or not and distant metastasis or not, the HASs' mRNA & protein differential expression all had no statistical significance (all P values >0.05). CONCLUSION:Different from other malignancy, HA and HASs (except for HAS3) may not play important roles in the biological progress of human RCCC.
| S-EPMC3587526 | biostudies-literature
Project description:The hereditary hearing-vision loss disease Usher syndrome (USH) is caused by defects in several proteins, most of which form an integrated protein network called Usher interactome. Harmonin/Ush1C is a master scaffold in the assembly of the Usher protein complexes, because harmonin is known to bind to every protein in the Usher interactome. However, the biochemical and structural mechanism governing the Usher protein complex formation is largely unclear. Here, we report that the highly-conserved N-terminal fragment of harmonin (N-domain) immediately preceding its PDZ1 adopts an autonomously-folded domain. We discovered that the N-domain specifically binds to a short internal peptide fragment of the cadherin 23 cytoplasmic domain. The structures of the harmonin N-domain alone and in complex with the cadherin 23 internal peptide fragment uncovered the detailed binding mechanism of this interaction between harmonin and cadherin 23. We further elucidated the harmonin PDZ domain-mediated cadherin 23 binding by solving the structure of the second harmonin PDZ domain in complex with the cadherin 23 carboxyl tail. The multidentate binding mode between harmonin and cadherin 23 provides a structural and biochemical basis for the harmonin-mediated assembly of stable tip link complex in the auditory hair cells.
| S-EPMC2667052 | biostudies-literature
Project description:Ordered conformations of proteoglycan-hyaluronic acid aggregates in the intercellular matrix in cartilage were observed by X-ray diffraction. The sodium salt form of three samples, (a) aggregated proteoglycan, (b) disaggregated proteoglycan and (c) reconstituted disaggregated proteoglycan, give essentially similar X-ray fibre-type diffraction photographs. The patterns correlate with the chondroitin 4-sulphate component and can be interpreted as twofold helical conformations, similar to that observed previously for the free acid form of chondroitin 4-sulphate (Isaac & Atkins, 1973). The information takes us one step nearer the situation found in cartilage in vivo.
| S-EPMC1168199 | biostudies-other
Project description:The interaction between proteoglycan and link protein extracted from bovine articular cartilage (15-18-month-old animals) was investigated in 0.5 M-guanidinium chloride. The proteoglycans, radiolabelled as the aggregate (A1 fraction), were fractionated by two 'dissociative' density-gradient centrifugations (A1D1D1) followed by a rate-zonal centrifugation (S1) to yield an A1D1D1S1 preparation. At least 65% of these proteoglycans were able to bind to hyaluronate, but only 52% were able to bind to link protein as assessed by chromatography on Sepharose CL-2B. Over 80% of the [3H]link-protein preparation, radiolabelled as the aggregate, was able to interact with proteoglycan as assessed by chromatography on Sepharose CL-4B. Equilibrium-boundary-centrifugation studies performed at low link-protein concentrations (2.42 x 10(-9) M-5.93 x 10(-8) M) were analysed by Scatchard-type plots and indicated a Kd of 1.5 x 10(-8) M and a stoichiometry, n = 0.56, i.e. approx. 56% of those proteoglycans capable of binding to link protein had a strong site for link protein if a 1:1 stoichiometry were assumed. However, experiments performed at higher link-protein concentrations (3.5 x 10(-7) M and 8 x 10(-7) M) yielded stoichiometry values which were link-protein-concentration-dependent. Non-equilibrium binding studies using chromatography on Sepharose CL-2B and rate-zonal centrifugation yielded apparent stoichiometries between 0.6 and 7.5 link-protein molecules per proteoglycan monomer as a function of increasing link-protein concentration. It was concluded that a proportion of the proteoglycan molecules had a strong site for binding a single link protein (Kd 1.5 x 10(-8) M) and that at high link-protein concentrations a weaker, open-ended, process of link-protein self-association nucleated upon the strong link-protein-proteoglycan complex occurred. Hyaluronate oligosaccharides appeared to abolish a proportion of this self-association (as observed by Bonnet, Dunham & Hardingham [(1985) Biochem. J. 228, 77-85] in a study of link-protein-hyaluronate-oligosaccharide interactions) so as to leave a link protein:proteoglycan stoichiometry of 2. It is not clear whether this second link-protein molecule binds directly to the proteoglycan or to the first link protein.
| S-EPMC1148641 | biostudies-other
Project description:Proteoglycan aggregates of cartilage are stabilized by the formation of a ternary complex between the G1 domain at the N-terminus of the proteoglycan monomer (aggrecan), link protein and hyaluronan polysaccharide. Both the G1 domain and link protein contain similar three-domain structures formed from an immunoglobulin fold and two proteoglycan tandem repeats, the arrangement of which had been investigated by neutron and synchrotron X-ray scattering [Perkins, Nealis, Dunham, Hardingham & Muir (1991) Biochemistry 30, 10708-10716]. Here, solution scattering was used to investigate the ternary complexes formed between a proteolytic fragment of proteoglycan monomer containing G1 (termed binding region), link protein and hyaluronan oligosaccharides containing either 34 or 450 saccharide units (HA34 and HA450). The ternary complex with HA34 had a neutron radius of gyration, RG, at infinite contrast not exceeding 5.5 nm. The ternary complex with HA34 had an X-ray cross-sectional radius of gyration Rxs of 2.4 nm and a neutron Rxs at infinite contrast of 2.00 nm. Since both were similar or larger than the Rxs for binding region (X-rays, 2.04 nm; neutrons, 1.84 nm) and link protein (neutrons, 0.8 nm), analyses showed that the cross-sectional mean width of the ternary complex is greater than those in each of the free proteins, i.e. the two proteins associated side-by-side. Similar results were obtained with HA450 complexed with binding region and with both binding region and link protein. This structural model was verified by hydrodynamic simulations of the experimental sedimentation coefficient of 5.5 S, which showed that a compact ternary-complex structure was formed. Although scattering curve simulations using small spheres were limited for the ternary complex with HA34 because of its approximate RG value, the scattering data were compatible with the formation of a compact complex formed by side-by-side contacts between G1 and link protein.
| S-EPMC1132775 | biostudies-other
Project description:The synthesis of link-stabilized proteoglycan aggregates by rabbit articular chondrocytes was investigated by [35S]sulphate labelling of primary monolayer cultures maintained for up to 21 days. (1) At all culture times the cells secreted a high-molecular-weight cartilage-type proteoglycan monomer of which 75%-80% formed aggregates with hyaluronic acid. (2) At 2 days of culture all of the aggregates were in link-stabilized form, but by 21 days only 5% were link-stabilized, as shown by displacement of monomers from the aggregate by hyaluronic acid oligosaccharides. (3) The addition of purified link protein to 21-day culture medium increased the proportion of link-stable aggregate from 5% to 70%. (4) Analysis of [3H]serine-labelled proteoglycan aggregates in the medium showed a marked decrease with culture time in the ratio of 3H-labelled link protein to 3H-labelled core protein present. The results suggest that the secretion of proteoglycan monomers and link protein by articular chondrocytes changes independently during prolonged monolayer culture.
| S-EPMC1152324 | biostudies-other