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Query: UNIPROT:P08758 (annexin V)
 9,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Annexin VI is an eight repeat member of the annexin family of proteins which are both water soluble and bind to negatively charged phospholipids in a calcium-dependent manner. Here we present a model for annexin VI based on fitting the three-dimensional structure of two annexin V molecules (Huber (1990) EMBO J. 9, 3867-3874) to the two-dimensional stain-excluding density of lipid-bound annexin VI (Newman (1989) J. Mol. Biol. 206, 213-219). Both annexin VI lobes could only be fitted with their convex faces closest to the lipid monolayer. This supports the hypothesis that annexin-lipid binding is mediated by the interaction between calcium bound to the loops protruding from the convex protein surface and phospholipid headgroups.
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PMID:A model of the structure of human annexin VI bound to lipid monolayers. 138 88

The distribution of annexin V isoforms (CaBP33 and CaBP37) and of annexin VI in bovine lung, heart, and brain subfractions was investigated with special reference to the fractions of these proteins which are membrane-bound. In addition to EGTA-extractable pools of the above proteins, membranes from lung, heart, and brain contain EGTA-resistant annexins V and VI which can be solubilized with detergents (Triton X-100 or Triton X-114). A strong base like Na2CO3, which is usually effective in extracting membrane proteins, only partially solubilizes the membrane-bound, EGTA-resistant annexins analyzed here. Also, only 50-60% of the Triton X-114-soluble annexins partition in the aqueous phase, the remaining fractions being recovered in the detergent-rich phase. Altogether, these findings suggest that, by an as yet unknown mechanism, following Ca(2+)-dependent association of annexin V isoforms and annexin VI with membranes, substantial fractions of these proteins remain bound to membranes in a Ca(2+)-independent way and behave like integral membrane proteins. These results further support the possibility that the above annexins might play a role in membrane trafficking and/or in the regulation of the structural organization of membranes.
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PMID:Membrane-bound annexin V isoforms (CaBP33 and CaBP37) and annexin VI in bovine tissues behave like integral membrane proteins. 153 Nov 31

Annexins represent a widespread family of Ca(++)-dependent phospholipid binding proteins. Although their precise functions are still unknown, they probably play an important role in cell regulation because they are major substrates for various growth factor receptor kinases. We characterized annexins in human skin using three different antisera raised against annexin II, annexin V, and a synthetic peptide that resembles the consensus sequence of all annexins. In normal human skin, using SDS-PAGE, two-dimensional gel electrophoresis and immunoblot analysis, we identified two major 34-kDa proteins and one 36-kDa protein, with respective isoelectric points of 6.5, 5.2, and 7.2-7.9. According to these criteria they were identified as annexins, I, V, and II, respectively. Minor 45-51 kDa and 68-kDa proteins with 6.1-6.7 and 6.8-7.1 isoelectric points were also present, and likely corresponded to annexins VII and VI, respectively. We investigated the ability of these proteins to bind phospholipids in the presence of calcium using liposomes formed from a mixture of phosphatidylserine and phosphatidylcholine. The cellular distribution of annexins in normal human skin was determined by immunofluorescence with antiannexin II and anti-annexin V antibodies. Labeling with both antibodies was observed predominantly at the cell membrane with some cytoplasmic staining also being apparent. Specificity was confirmed by the absence of staining using pre-immune sera or after the absorption of the antibodies with their corresponding antigens. These proteins were also characterized in vitro in a reconstituted human skin model. All were present in this system except annexin VI and VII, which were lost after phospholipid purification. Further experiments should now be carried out using this system to clarify the role and regulation of these proteins within the epidermis.
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PMID:Characterization and subcellular localization of calcium-dependent phospholipid binding proteins (annexins) in normal human skin and reconstituted epidermis. 153 82

Calphobindin-II (CPB-II, annexin VI), is a calcium dependent phospholipid binding protein that can be classified as a member of the annexin family. The phospholipid-binding properties of CPB-II were investigated by measuring the binding constants of [125I]-CPB-II using phospholipid vesicles consisting of 80% phosphatidylcholine and 20% phosphatidylserine. A dissociation constant (Kd) of CPB-II with the phospholipid vesicles was determined to be 0.2 to 0.3 nM in the presence of Ca2+ ranging from 0.3 to 30 mM. The number of CPB-II capable of binding to the phospholipid vesicles at 0.3 mM Ca2+ decreased to about 1/2 in the presence of Ca2+ of more than 1 mM. Prothrombin and factor X were effective in competing with the binding of CPB-II to the phospholipid vesicles, although their affinities were lower by two or three orders of magnitude than that of unlabeled CPB-II at 30 nM Ca2+. Competitive effects of CPB-II, calphobindin-I (CPB-I, annexin V) and calphobindin-III (CPB-III, annexin III) on binding of [125I]-CPB-II to phospholipid vesicles, were similarly observed.
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PMID:Phospholipid-binding properties of calphobindin-II(annexin VI), anticoagulant protein from human placenta. 183 15

Two calcium-independent phospholipases isolated from guinea pig pancreas (lipase Ia, 37 kDa) and from guinea pig intestine (phospholipase B, 97 kDa) have been used to probe the mechanism of phospholipase inhibition by lipocortin. In the presence of calcium, both enzymes were inhibited by lipocortin I in a manner very similar to the inhibition of pig pancreas phospholipase A2. By using phospholipases that lack a requirement for calcium, we have for the first time been able to dissociate enzymatic activity from the role of calcium in the inhibitory process. It was found that lipocortin was without effect against phospholipase A1 and phospholipase B in the absence of calcium, under which conditions the inhibitory protein is unable to interact with anionic phospholipid surfaces. The same behavior toward phospholipase A1 was observed with two other related proteins, endonexin II or lipocortin V, and p68/67-kDa calelectrin or lipocortin VI. Together with the observation that lipocortins are active only in the presence of limited amounts of substrate, these data give further support to the "surface depletion model" of lipocortin inhibition, rather than to a mechanism involving a direct interaction between enzyme and inhibitor.
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PMID:Calcium-independent phospholipases from guinea pig digestive tract as probes to study the mechanism of lipocortin. 213 21

Calcium-dependent phospholipid binding and phospholipase A2 inhibitory proteins were isolated from human mononuclear cells. Lipocortins I and II were present whereas lipocortin IV (endonexin I) was not. The other proteins were purified to homogeneity and shown to have molecular masses of 35, 36, 32 and 73 kDa. The 36-kDa and 73-kDa proteins are related, the smaller appears to be part of the larger. The 73-kDa protein is related to the 67-kDa calelectrin and to lipocortin VI; the 32-kDa protein is different from endonexin I but related to chromobindin 7 and to lipocortin V. The 35-kDa protein has been identified by tryptic peptide sequencing as lipocortin III. All these proteins inhibit phospholipase A2 activity in vitro and the three smaller ones inhibit the [3H]arachidonic acid release from prelabelled monocytes induced by the calcium ionophore A23187 in a dose-dependent manner.
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PMID:Identification and characterization of phospholipase A2 inhibitory proteins in human mononuclear cells. 213 36

Immunoblot analyses and ultrastructural immunogold studies have been conducted on annexins in the secretory ameloblasts and odontoblasts of the rat incisor. Annexins I and II were seen in the soluble and particulate fractions of the enamel-related portion but not in the dentin-related portion. These proteins were visualized in the cytosol, near to the plasma membrane of Tomes' processes and in secretory vesicles in the ameloblasts. The forming enamel was also labeled. Annexins III, VI an V were detected in both the soluble and particulate fractions of the enamel-and dentin-related portions. Annexin IV was mainly localized in the proximal and distal areas of the secretory ameloblasts and virtually absent from in the supranuclear area. Annexin V was mainly detected in the cytosol of the cells and to a lesser extent near the plasma membrane. Annexin VI was mainly detected in the particulate fraction of enamel- and dentin-related portions. It was seen in the mitochondria and in the subplasmalemmal undercoat. All these proteins may play a role in exocytosis and endocytosis. They are implied in the regulation of cell calcium, but not in the transfer of calcium through the cells in the direction of the forming enamel and dentin, except annexins I and II since they are both present in the secretory vesicles and in the forming enamel.
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PMID:Annexins I-VI in secretory ameloblasts and odontoblasts of rat incisor. 215 31

Four proteins of the lipocortin family, lipocortin I (35 kDa), lipocortin II (36 kDa), lipocortin V (32 kDa) and lipocortin VI (67-70 kDa), were identified in the cytosols of 2-day-old cultures of thyroid cells. Only lipocortin I was phosphorylated in vitro in fully differentiated, thyroid stimulating hormone-treated cells (0.1 mU/ml). Protein kinase C was the only kinase activity which phosphorylated lipocortin I. Phosphorylation shifted its pI from 6.9 to 6.6. The in vitro phosphorylation of lipocortin I was impaired in cultures exposed for 2 days to phorbol ester (10(-7) M), although it was present in both the cytosol and the particulate fraction of these cells.
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PMID:Identification of four lipocortin proteins and phosphorylation of lipocortin I by protein kinase C in cytosols of porcine thyroid cell cultures. 253 54

Four calcium and phospholipid binding proteins purified from mononuclear cells were characterized for PKC and EGF phosphorylation, actin binding capacity, and partial tissue distribution. Those named 35K, 32K, and 73K are equivalent, respectively, to lipocortin III, endonexin II and the 67 kDa calelectrin; 36K is a fragment of 73K. After purification, 35K and 73K were phosphorylated by protein kinase C in vitro but 36K nor 32K were not. None were phosphorylated by the epidermal growth factor receptor kinase in vitro; 73K bound F-actin in a calcium-dependent manner, whereas 35K, 36K, and 32K did not. Using Western blotting analysis, 32K and 73K were detected in high amounts in human lymphocytes, monocytes, liver, and placenta and in rat adrenal medulla; but 32K was not detected in polymorphonuclear cells, and 36K and 35K were detected in high amounts only, respectively, in human blood lymphocytes and polymorphonuclear cells. Thus, 32K and 73K appear to have a wide tissue distribution, whereas 35K has a much more restricted distribution.
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PMID:Further characterization of four lipocortins from human peripheral blood mononuclear cells. 255 Apr 91

The calcium-dependent interaction of several annexins with membranes was studied. A novel technique was developed that allowed estimation of calcium binding to aggregating systems. This consisted of immobilized phospholipids on phenyl-Sepharose. Proteins associated with this affinity gel in the presence of radioactive calcium and were eluted with the same buffer containing excess EGTA. This produced an elution profile with a peak of excess calcium. Protein extinction coefficients were estimated in order to quantitate the protein more accurately. Association of annexin II with the membrane was of very high affinity and involved a calcium stoichiometry of 11 +/- 1 at 12.5 microM free Ca2+ and 10 +/- 2 at 50 microM free Ca2+. (AII)2(p11)2, a heterotetramer of two annexin II and two p11 subunits, bound 12 +/- 1 Ca2+ at 12.5 microM Ca2+ and 15 +/- 1 Ca2+ at 50 microM Ca2+. These stoichiometries showed a pattern of "all or none" calcium binding where the number of calcium ions bound to a protein-membrane complex was virtually independent of the free calcium concentration or the density of protein on the membrane. (AII)2(p11)2 contains two annexin II subunits so that calcium stoichiometry was not directly related to the number of potential sites. (AII)2(p11)2 required less calcium to support membrane binding than did annexin II. Thus, dimerization of the membrane binding unit may be needed for annexins to function at intracellular calcium levels. Annexin VI contains twice as many putative calcium binding units as annexin V and the same pattern of behavior occurred for this pair of proteins. At 25 microM free calcium, (AII)2(p11)2 alone bound no detectable calcium (< 0.1 mol of calcium/mol of protein) and annexin II bound only 0.3-0.6 calcium ions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Calcium and membrane-binding properties of monomeric and multimeric annexin II. 794 30


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