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Query: UNIPROT:P02749 (beta2-glycoprotein I)
 836 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The general hypothesis for the biological function of beta 2-glycoprotein I is that it neutralizes all negatively charged macromolecules that might enter the bloodstream and diminishes unwanted activation of the blood coagulation. In the present study we report that beta 2-glycoprotein I inhibits the activation of the contact phase system of the intrinsic pathway of blood coagulation. Activation was accomplished by an ellagic acid-phospholipid suspension (Cephotest) and measured by the appearance of amidolytic activity using the chromogenic substrate H-D-Pro-Phe-Arg-p-nitroanilide (S-2302). This inhibitory effect of beta 2-glycoprotein I was observed both when Cephotest was preincubated with beta 2-glycoprotein I and when the amount of beta 2-glycoprotein I in plasma was increased by addition of beta 2-glycoprotein I to either normal or beta 2-glycoprotein I-deficient plasma. The inhibitory effect of beta 2-glycoprotein I on the contact phase activation could be one of the physiological functions of this protein.
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PMID:beta 2-Glycoprotein I: a plasma inhibitor of the contact activation of the intrinsic blood coagulation pathway. 405 28

In 48 men occupationally exposed to CS2 the following glycoproteins were estimated in blood serum, using radial immunodiffusion on M-Partigen plates: alpha1-acid glycoprotein, alpha1-antitrypsin, alpha2-HS-glycoprotein, alpha2-macroglobulin, Gc glycoprotein, hemopexin, haptoglobin, ceruluplasmin and beta2-glycoprotein I. The studies indicated a highly statistically significant increase of: alpha1-acid--glycoprotein and Gc glycoprotein, and decrease of: alpha1-antitrypsins, alpha2-HS--glycoprotein and beta2-glycoprotein. The level of the remaining glycoproteins was normal.
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PMID:[Blood serum glycoproteins in men exposed to carbon disulfide]. 616 75

Several different binding mechanisms appear to be involved in the binding of beta 2-glycoprotein I to biological membranes. One of these mechanisms is a hydrophilic interaction between negatively-charged phospholipids in the membrane and histidine residues in beta 2-glycoprotein I. This mechanism seems to be involved in binding of the protein to mitochondria but not to platelets. Another mechanism may involve a site on beta 2-glycoprotein I, which binds to the steroid ring system particularly to such steroids not having a 7-hydroxy group. This type of binding may be involved in the interaction between beta 2-glycoprotein I and platelets as well as mitochondria.
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PMID:Characterization of the interaction between beta 2-glycoprotein I and mitochondria, platelets, liposomes and bile acids. 636 Jul 44

beta 2-Glycoprotein I (beta 2GI) has recently been identified as a component of circulating plasma lipoproteins. The metabolic role of this apolipoprotein is not known with certainty; it has been reported that beta 2GI has a high affinity for triglyceride-rich particles, causing their selective precipitation by detergents, and activates lipoprotein lipase in the in vitro hydrolysis of artificial lipid emulsions. In the present report, we have evaluated the secondary, tertiary, and quaternary structure of lipid-free beta 2GI. The weight average molecular weight of beta 2GI, as determined by sedimentation equilibrium measurements, was 43,000 in the presence and absence of denaturing agents. Thus, in contrast to other apolipoproteins, apolipoprotein H (apo-H) does not self-associate in aqueous solution. The circular dichroic spectra of apo-H is unusual in that there are no strong negative bands in the far-ultraviolet region of the spectrum; there is a weak positive maximum at 235 nm and a relatively weak negative maximum at 205 nm. Treatment with guanidinium chloride results in a loss of the positive band with only minor changes in the intensity of the band at 205 nm. Apolipoproteins A-I, A-II, C-I, and E, in contrast, have a secondary structure that contains a high percentage of residues in an alpha-helical configuration and undergo major changes in structure at low concentrations of guanidinium chloride. Highly flexible proteins, such as apolipoproteins A-I, A-II, and C-I, absorb rapidly and reversibly to air-water interfaces, whereas more rigid proteins, such as the classical globular proteins, interact with the interface more slowly and irreversibly. This difference is due to the loosely folded tertiary structure of apolipoproteins and the ease with which they can change structure to accommodate a given environment. The surface activity of beta 2GI at neutral pH resembles that of typical globular proteins. Treatment with acid or base, although causing only minor changes in the circular dichroic spectra, resulted in major increases in the rate of absorption to an air-water interface; under these conditions the rates of absorption were similar to that found for apolipoprotein A-I. These results are consistent with a more flexible structure for beta 2GI in acid or base that resembles other loosely folded apolipoproteins. beta 2GI associates with plasma lipoproteins and satisfies all of the criteria to be classified as an apolipoprotein. The secondary, tertiary, and quaternary structure of beta 2GI is, however, quite different from that of other well characterized apolipoproteins. This difference in structure would be expected to affect protein-lipid interactions; the relationship between apo-H and other apolipoproteins may be similar to that proposed for integral versus peripheral membrane proteins.
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PMID:beta 2-Glycoprotein I. Molecular properties of an unusual apolipoprotein, apolipoprotein H. 640 35

The binding characteristics of the human serum protein beta 2-glycoprotein-I, also called apolipoprotein H, with multilamellar phospholipid vesicles has been studied. It was found that beta 2-G-I is not or almost not bound to the "neutral" phospholipids phosphatidylcholine (PC), phosphatidylethanolamine (PE) and sphingomyelin (SM). The negatively charged compounds phosphatidylserine (PS) and phosphatidylinositol (PI) interact strongly with beta 2-G-I. In terms of phospholipid concentration the binding to PS is about one order of magnitude greater than to PI. The binding capacity is influenced by several parameters such as the molarity of buffer, presence of mono- or divalent cations as well as ethylenediaminotetraacetic acid (EDTA). Proteins like bovine serum albumin (BSA), human serum albumin (HSA) or horse gamma-globulin (HGG) influence the binding also in a concentration dependent manner.
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PMID:beta 2-Glycoprotein-I (apolipoprotein H) interactions with phospholipid vesicles. 642 35

The combination of gel permeation chromatography and high-performance liquid chromatography proves to be very effective for the purification of high-molecular-weight glycopeptides containing a single glycan, that have been difficult to separate by other procedures. In order to facilitate comparison of the chromatographic properties of glycopeptides derived from a variety of proteins and having different structures, identical procedures were used for their purification. The method was applied to a series of human plasma proteins, including immunoglobulin D, ceruloplasmin, hemopexin, beta-2-glycoprotein I, 3.1S alpha-2-leucine-rich glycoprotein, and alpha-1-B-glycoprotein. All the purified glycopeptides were placed in the protein structure of these plasma proteins. In several cases the carbohydrate structure has been determined by collaborating groups. Immunoglobulin D is the first example of a glycoprotein whose entire primary structure has been defined by utilizing a a single protein source. Furthermore, hemopexin and 3.1S alpha-2-leucine-rich glycoprotein were both found to contain GalN oligosaccharide, which had not previously been identified in these proteins. The method was also used to identify the oligosaccharide that is missing in a carbohydrate variant of ceruloplasmin.
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PMID:Purification of glycopeptides of human plasma proteins by high-performance liquid chromatography. 653 Apr 29

We have determined the complete amino acid sequence of beta 2-glycoprotein I (Mr, congruent to 50,000), a human plasma protein that is associated with lipids and binds to platelets but whose function is not yet known. The protein consists of 326 amino acids and has five attached glucosamine-containing oligosaccharides. The protein is rich in cysteine and proline, and the sequence is notable for the frequent occurrence of Cys-Pro linkages at regular intervals. Computerized analysis of the sequence reveals five consecutive homologous segments in which cysteine, proline, and tryptophan appear to be highly conserved. This suggests that beta 2-glycoprotein I may have evolved by repeated duplications of a gene coding for a 60-amino acid segment of protein.
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PMID:Complete amino acid sequence of human plasma beta 2-glycoprotein I. 658 78

Beta 2-glycoprotein-I (apolipoprotein H) is an activator of the lipoprotein lipase. The concentration of beta 2-glycoprotein-I in the blood serum was determined with the help of the radial immunodiffusion. In patients with hyperlipoproteinaemia of type IIa and IIb, arteriosclerotic obstructive disease or diabetes mellitus the beta 2-glycoprotein-I-concentrations were increased. In hyperlipoproteinaemia of type IV can be concluded to a relative beta 2-glycoprotein-I-deficiency.
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PMID:[Beta 2 glycoprotein I analysis in patients with hyperlipoproteinemia, arteriosclerotic occlusive disease and diabetes mellitus]. 661 92

Reversed-phase high-performance liquid chromatography (HPLC) with a linear elution gradient of 1-propanol in 0.1% aqueous trifluoroacetic acid was used to purify cyanogen bromide fragments from the human plasma protein beta-2-glycoprotein I. The fragments, ranging from 33 to 119 amino acids in length, were obtained in sufficient purity and yield for automated sequence analysis and enzymatic digestion. One fragment, which contained most of the carbohydrate, could be isolated as an aggregate or as two heterogeneous monomers. The elution of this fragment was much earlier than expected on the basis of its retention coefficient calculated from amino acid composition. Our results demonstrate the applicability of recently developed HPLC techniques to the separation of cyanogen bromide fragments from a carbohydrate-rich glycoprotein whose structure is not completely known.
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PMID:Purification of cyanogen bromide fragments from beta-2-glycoprotein I by high-performance liquid chromatography. 663 Mar 61

Washed human platelets were preincubated with 0-300 micrograms/ml human beta 2-glycoprotein I and the effect of this on the adenylate cyclase activity (EC.4.6.1.1.) was studied. Adenylate cyclase activity could be increased 2-3 fold. The same degree of activation was seen when low concentrations of prostaglandin E1 (1 microM) had been present concomitant with beta 2-glycoprotein I during preincubation. The dose-response curves of the adenylate cyclase activity measured as a function of the beta 2-glycoprotein I concentration were S-shaped in the absence of prostaglandin E1 and hyperbolic in its presence. The results suggest a biological function of beta 2-glycoprotein I as a compound conserving and activating the membrane-bound adenylate cyclase.
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PMID:Effect of beta 2-glycoprotein I on the activity of adenylate cyclase in platelet membranes. 668 48


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