Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.3.3.1 (citrate synthase)
 4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clusterin is the first well characterized, constitutively secreted extracellular chaperone that binds to exposed regions of hydrophobicity on non-native proteins. It may help control the folding state of extracellular proteins by targeting them for receptor-mediated endocytosis and intracellular lysosomal degradation. A notable feature of secreted clusterin is its heavy glycosylation. Although carbohydrate comprises approximately 20-25% of the total mass of the mature molecule, its function is unknown. Results from the current study demonstrate that deglycosylation of human serum clusterin had little effect on its overall secondary structure content but produced a small increase in solvent-exposed hydrophobicity and enhanced the propensity of the molecule to aggregate in solution. These changes were associated with increased binding to a variety of ligands but did not substantially impact the ability of clusterin to inhibit heat-induced precipitation of citrate synthase. Evidence suggesting that the normally conjugated sugars are important in the interaction of secreted clusterin with a lectin-type receptor on liver cells is also presented. Bulk expression of fully processed, glycosylated clusterin in mammalian cells is difficult, often producing inappropriately disulfide-bonded high molecular weight aggregates; this has hampered previous studies aimed at identifying those regions of the molecule important in its chaperone action. The current results suggest that it may be possible in the future to study the structure and chaperone function of clusterin using recombinant protein (lacking sugars) conveniently bulk-expressed in bacteria.
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PMID:Effects of glycosylation on the structure and function of the extracellular chaperone clusterin. 1726 Sep 71

Clusterin (CLU) is a potent extracellular chaperone that inhibits protein aggregation and precipitation otherwise caused by physical or chemical stresses (e.g. heat, reduction). This action involves CLU forming soluble high molecular weight (HMW) complexes with the client protein. Other than their unquantified large size, the physical characteristics of these complexes were previously unknown. In this study, HMW CLU-citrate synthase (CS), HMW CLU-fibrinogen (FGN), and HMW CLU-glutathione S-transferase (GST) complexes were generated in vitro, and their structures studied using size exclusion chromatography (SEC), ELISA, SDS-PAGE, dynamic light scattering (DLS), bisANS fluorescence, and circular dichroism spectrophotometry (CD). Densitometry of Coomassie Blue-stained SDS-PAGE gels indicated that all three HMW CLU-client protein complexes had an approximate mass ratio of 1:2 (CLU:client protein). SEC indicated that all three clients formed complexes with CLU>or=4x10(7) Da; however, DLS estimated HMW CLU-FGN to have a diameter of 108.57+/-18.09 nm, while HMW CLU-CS and HMW CLU-GST were smaller with estimated diameters of 51.06+/-6.87 nm and 52.61+/-7.71 nm, respectively. Measurements of bisANS fluorescence suggest that the chaperone action of CLU involves preventing the exposure to aqueous solvent of hydrophobic regions that are normally exposed by the client protein during heat-induced unfolding. CD analysis indicated that, depending on the individual client protein, CLU may interact with a variety of intermediates on protein unfolding pathways with different amounts of native secondary structure. In vivo, soluble complexes like those studied here are likely to serve as vehicles to dispose of otherwise dangerous aggregation-prone misfolded extracellular proteins.
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PMID:Structural characterization of clusterin-chaperone client protein complexes. 1953 39

The global proteome of sperm and seminal plasma of fertile stallions was investigated to determine whether associations with relative in vivo fertility exist. Seven stallions at stud in a commercial breeding station were collected throughout the breeding season and bred to a total of 164 mares to determine conception rates. On three occasions during the breeding season, raw semen was obtained from a regular collection for proteomic analysis using two-dimensional electrophoresis and also assessed for routine semen quality end points. First cycle conception rate was negatively related to ejaculate volume (r = -0.43, P = 0.05) and total IGF1 content (ng) per ejaculate (r = -0.58, P = 0.006), whereas overall pregnancy rate was positively related to sperm concentration (r = 0.56, P = 0.01). The abundance of three proteins known to be involved in carbohydrate metabolism in sperm was positively related to fertility. Furthermore, the abundance of four seminal plasma proteins were identified as being negatively related to fertility; these were identified as kallikrein-1E2 (KLK2), clusterin, and seminal plasma proteins 1 (SP1) and 2 (SP2). Abundance of cysteine-rich secretory protein 3 (CRISP3) was positively related to first cycle conception rate (r = 0.495, P = 0.027) and may provide a good marker of fertility. Based on stepwise regression analysis, clusterin and SP1 in seminal plasma together with sperm citrate synthase were predictive of fertility (r = 0.77, P < 0.0001). This study identified proteins within sperm and seminal plasma that could serve as biomarkers of semen quality and fertility in stallions.
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PMID:Biomarkers of in vivo fertility in sperm and seminal plasma of fertile stallions. 2058 75