Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A membrane-bound, haemolytic phospholipase A(2) (PLA(2)) activity was detected in clinical strains of Campylobacter concisus isolated from children with gastroenteritis. The clinical strains were assigned into two molecular groups (genomospecies) based on PCR amplification of their 23S rDNA. This calcium-dependent, heat-stable, haemolytic PLA(2) activity was detected in strains from both genomospecies. A crude haemolysin extract (CHE) was initially prepared from cellular outer-membrane proteins of these isolates and was further fractionated by ultrafiltration. The haemolytic activity of the extracted fraction (R30) was retained by ultrafiltration using a 30 kDa molecular mass cut-off filter, and was designated haemolysin extract (HE). Both CHE and HE had PLA(2) activity and caused stable vacuolating and cytolytic effects on Chinese hamster ovary cells in tissue culture. Primers for the conserved region of pldA gene (phospholipase A gene) from Campylobacter coli amplified a gene region of 460 bp in all tested isolates, confirming the presence of a homologous PLA gene sequence in C. concisus. The detection of haemolytic PLA(2) activity in C. concisus indicates the presence of a potential virulence factor in this species and supports the hypothesis that C. concisus is a possible opportunistic pathogen.
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PMID:Characterization of a haemolytic phospholipase A(2) activity in clinical isolates of Campylobacter concisus. 1515 Mar 26

Phospholipase A(2) (PLA(2)) hydrolyzes glycerophospholipids to free fatty acid and lyso-phospholipid, which serve as precursors for the biosynthesis of eicosanoids and other lipid-derived mediators of inflammation and allergy. PLA(2) activity strongly increases upon binding to the surface of aggregated phospholipid. The N-terminal approximately ten residue alpha-helix of certain PLA(2) isoforms plays important roles in the interfacial activation of the enzyme by providing residues for membrane binding of PLA(2) and by contributing to the formation of the substrate-binding pocket. However, the relative contributions of the N-terminal alpha-helix and the rest of the protein in membrane binding of PLA(2) and its productive-mode orientation at the membrane surface are not well understood. Here we use a variety of biophysical approaches to determine the role of the N-terminal helix in membrane binding strength, orientation, and activity of human pancreatic PLA(2). While the full-length PLA(2) binds to membranes with a defined orientation, an engineered PLA(2) fragment DeltaN10 that lacks the N-terminal ten residues binds to membranes with weaker affinity and at random orientation, and exhibits approximately 100-fold lower enzymatic activity compared to the full-length PLA(2), indicating the key role of the N terminus in PLA(2) function. The results of polarized infrared spectroscopic experiments permit determination of the orientation of membrane-bound PLA(2) and identification of its interfacial binding surface. Moreover, the full-length PLA(2) demonstrates increased conformational flexibility in solution and is stabilized upon membrane binding, while the DeltaN10 fragment is more rigid than the full-length PLA(2) both in free and membrane-bound states. Our results suggest that the N-terminal alpha-helix supports the activation of PLA(2) by (a) enhancing the membrane binding strength, (b) facilitating a productive-mode orientation of PLA(2) at the membrane surface, and (c) conferring conformational integrity and plasticity to the enzyme.
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PMID:The N-terminal alpha-helix of pancreatic phospholipase A2 determines productive-mode orientation of the enzyme at the membrane surface. 1550 3

The phospholipase A(2) (PLA(2)) enzymes are activated by binding to phospholipid membranes. Although the N-terminal alpha-helix of group I/II PLA(2)s plays an important role in the productive mode membrane binding of the enzymes, its role in the structural aspects of membrane-induced activation of PLA(2)s is not well understood. In order to elucidate membrane-induced conformational changes in the N-terminal helix and in the rest of the PLA(2), we have created semisynthetic human group IB PLA(2) in which the N-terminal decapeptide is joined with the (13)C-labeled fragment, as well as a chimeric protein containing the N-terminal decapeptide from human group IIA PLA(2) joined with a (13)C-labeled fragment of group IB PLA(2). Infrared spectral resolution of the unlabeled and (13)C-labeled segments suggests that the N-terminal helix of membrane-bound IB PLA(2) has a more rigid structure than the other helices. On the other hand, the overall structure of the chimeric PLA(2) is more rigid than that of the IB PLA(2), but the N-terminal helix is more flexible. A combination of homology modeling and polarized infrared spectroscopy provides the structure of membrane-bound chimeric PLA(2), which demonstrates remarkable similarity but also distinct differences compared with that of IB PLA(2). Correlation is delineated between structural and membrane binding properties of PLA(2)s and their N-terminal helices. Altogether, the data provide evidence that the N-terminal helix of group I/II PLA(2)s acts as a regulatory domain that mediates interfacial activation of these enzymes.
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PMID:Evidence for the regulatory role of the N-terminal helix of secretory phospholipase A(2) from studies on native and chimeric proteins. 1610 16

The Yersinia pestis proteome was studied as a function of temperature and calcium by two-dimensional differential gel electrophoresis. Over 4,100 individual protein spots were detected, of which hundreds were differentially expressed. A total of 43 differentially expressed protein spots, representing 24 unique proteins, were identified by mass spectrometry. Differences in expression were observed for several virulence-associated factors, including catalase-peroxidase (KatY), murine toxin (Ymt), plasminogen activator (Pla), and F1 capsule antigen (Caf1), as well as several putative virulence factors and membrane-bound and metabolic proteins. Differentially expressed proteins not previously reported to contribute to virulence are candidates for more detailed mechanistic studies, representing potential new virulence determinants.
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PMID:Proteomic characterization of Yersinia pestis virulence. 1629 90

Matrix metalloproteinases (MMPs) are members of an enzyme family that require a zinc ion in their active site for catalytic activity. MMPs are critical for maintaining tissue allostasis. MMPs are active at neutral pH and can therefore catalyze the normal turnover of extracellular matrix (ECM) macromolecules such as the interstitial and basement membrane collagens, proteoglycans such as aggrecan, decorin, biglycan, fibromodulin and versican as well as accessory ECM proteins such as fibronectin. Members of the MMP family include the "classical" MMPs, the membrane-bound MMPs (MT-MMPs) the ADAMs (a disintegrin and metalloproteinase; adamlysins) and the ADAMTS (a disintegrin and metalloproteinase with thrombospondin motif). There are more than 20 members in the MMP and ADAMTS family including the collagenases, gelatinases, stromelysins, some elastases and aggrecanases. Adamlysins are membrane-bound MMPs that also degrade aggrecan, but more importantly, one ADAM family member (i.e.ADAM-17) is a tumor necrosis factor-alpha (TNF-alpha)-converting enzyme (TACE) that activates pro-TNF-alpha. Most of the MMPs are synthesized as inactive latent enzymes. Conversion to the active enzyme is generally mediated by activator systems that include plasminogen activator or the pro-hormone convertase, furin. MMP activity is regulated by a group of endogenous proteins, called, tissue inhibitor of metalloproteinases (TIMPs) that bind to active and alternative sites of the activated MMP. Significant advances have occurred in the understanding of the regulation of MMPs, ADAMs and ADAMTSs gene expression. In addition, development of MMP inhibitors to study MMP structure/function relationships spawned many studies to determine the effectiveness of MMP inhibitors in regulating abnormal connective tissue turnover. In addition, development of MMP null mice carrying specific MMP deletions has provided an opportunity to explore the role of MMPs in normal development as well as in such diverse conditions and diseases as skeletal dysplasias, coronary artery and heart disease, arthritis, cancer, and brain disorders.
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PMID:Matrix metalloproteinases (MMPs) in health and disease: an overview. 1636 48

Expression of the Ca(2+)-dependent phospholipids binding protein annexin A2 (ANX2) in the brain is thought to be largely associated with brain pathological conditions such as tumor, inflammation, and neurodegeneration. The recent findings that ANX2 heterotetramer is involved in learning and neuronal activities necessitates a systematic investigation of the physiological expression of ANX2 in the brain. With combination of in situ hybridization and immunohistochemistry, ANX2 mRNA and protein were specifically detected in a group of GABAergic interneurons throughout the brain. Although ANX2 was absent from the interior of pyramidal neurons, it was found on the membrane and seemly the extracellular space of those neurons, where they closely co-localized with glutamate decarboxylase terminals. In cultured developing neurons, ANX2 was present at high concentrations in the growth cones co-distributing with several growth-associated proteins such as growth associated protein 43 (GAP43), turned on after division/Ulip/CRMP (TUC-4), tubulin, and tissue-plasminogen activator. It then became predominantly distributed on the membrane and mostly in axonal branches as neurons grew and extended synaptic networks. ANX2 was also secreted from cultured neurons, in a membrane-bound form that was Ca(2+)-dependent, which was significantly increased by neuronal depolarization. These results may have implications in the function and regulatory mechanism of ANX2 in the normal brain.
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PMID:Expression of annexin A2 in GABAergic interneurons in the normal rat brain. 1731

Plant heterotrimeric G-proteins are involved in a variety of signaling pathways, though only one alpha and a few betagamma isoforms of their subunits exist. In isolated plasma membranes of California poppy (Eschscholzia californica), the plant-specific Galpha subunit was isolated and identified immunologically and by homology of the cloned gene with that of several plants. In the same membrane, phospholipase A(2) (PLA(2)) was activated by yeast elicitor only if GTPgammaS (an activator of Galpha) was present. From the cholate-solubilized membrane proteins, PLA(2) was co-precipitated together with Galpha by a polyclonal antiserum raised against the recombinant Galpha. In this immunoprecipitate and in the plasma membrane (but not in the Galpha-free supernatant) PLA(2) was stimulated by GTPgammaS. Plasma membranes and immunoprecipitates obtained from antisense transformants with a low Galpha content allowed no such stimulation. An antiserum raised against the C-terminus (which in animal Galphas is located near the target coupling site) precipitated Galpha without any PLA(2) activity. Using non-denaturing PAGE, complexes of solubilized plasma membrane proteins were visualized that contained Galpha plus PLA(2) activity and dissociated at pH 9.5. At this pH, PLA(2) was no longer stimulated by GTPgammaS. It is concluded that a distinct fraction of the plasma membrane-bound PLA(2) exists in a detergent-resistant complex with Galpha that can be dissociated at pH 9.5. This complex allows the Galpha-mediated activation of PLA(2).
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PMID:Regulatory interaction of the Galpha protein with phospholipase A2 in the plasma membrane of Eschscholzia californica. 1791 11

It is well known that the Escherichia coli inner membrane-bound protease DegS is a periplasmic stress sensor for unfolded outer membrane proteins (OMPs). Previous studies have also shown that the outer membrane protease OmpT activates plasminogen in vitro and this may be exploited by bacteria in the course of pathogenesis. However, there has been no research on the plasminogen activation ability of the important periplasmic protein DegS. Accordingly, in this study, the whole-length and truncated degS genes were separately overexpressed in Escherichia coli, the recombinant proteins purified by affinity chromatography, and their plasminogen activator role tested in vitro. The results suggested that the whole-length DegS was able to activate plasminogen on a plasma plate. The truncated form of DegS (residues 80-345), designated delta DegS, also acted as a plasminogen activator, as confirmed by different assays. The serine protease property of delta DegS was verified based on the complete inhibition of its enzyme activity by PMSF (phenylmethanesulfonyl fluoride). Therefore, the present results indicate that DegS is a plasminogen activator in vitro.
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PMID:Abridged region from Escherichia coli periplasmic stress sensor DegS acts as plasminogen activator in vitro. 1805 Dec 69

Matrilysin (matrix metalloproteinase-7) plays important roles in tumor progression. It was previously found that matrilysin binds to the surface of colon cancer cells to promote their metastatic potential. In this study, we identified annexin II as a novel membrane-bound substrate of matrilysin. Treatment of human colon cancer cell lines with active matrilysin released a 35 k Da annexin II form, which lacked its N-terminal region, into the culture supernatant. The release of the 35 k Da annexin II by matrilysin was significantly enhanced in the presence of serotonin or heparin. Matrilysin hydrolyzed annexin II at the Lys9-Leu10 bond, thus dividing the protein into an N-terminal nonapeptide and the C-terminal 35 k Da fragment. Annexin II is known to serve as a cell surface receptor for tissue-type plasminogen activator (tPA). Although the matrilysin treatment liberated the 35 k Da fragment of annexin II from the cell surface, it significantly increased tPA binding to the cell membrane. A synthetic N-terminal nonapeptide of annexin II bound to tPA more efficiently than intact annexin II. This peptide formed a heterodimer with intact annexin II in test tubes and on cancer cell surfaces. These and other results suggested that the nonapeptide generated by matrilysin treatment might be anchored to the cell membrane, possibly by binding to intact annexin II, and interact with tPA via its C-terminal lysine. It is supposed that the cleavage of cell surface annexin II by matrilysin contributes to tumor invasion and metastasis by enhancing tPA-mediated pericellular proteolysis by cancer cells.
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PMID:Matrilysin (matrix metalloprotease-7) cleaves membrane-bound annexin II and enhances binding of tissue-type plasminogen activator to cancer cell surfaces. 1872 Nov 40

Coupling factor 6 (CF6) is composed of 76 amino acids and is present in the peripheral stalk of mitochondrial ATP synthase. The generation of CF6 is positively regulated by tumor necrosis factor alpha and shear stress via nuclear factor kappaB, and by high glucose via protein kinase C and p38 mitogen-activated protein kinase. CF6 is released outside of the cells from vascular endothelial cells, and binds to the beta-subunit of the plasma membrane-bound ATP synthase in vascular endothelial cells and leads to intracellular acidosis. CF6 produces vasoconstriction, and the biological active site resides at the C-terminal portion. CF6 suppresses prostacyclin generation via inhibition of cytosolic phospholipase A(2). CF6 also suppresses nitric oxide synthase activity via an increase in asymmetric dimethylarginine and a decrease in platelet/endothelial cell adhesion molecule-1. CF6 induces the gene and protein expression of proatherogenic molecules such as endothelin 2, urokinase type plasminogen activator receptor, estrogen receptor beta, a soluble short form of vascular endothelial growth factor receptor-1, and lectin-like oxidized low-density lipoprotein receptor-1. The plasma level of CF6 is elevated in patients with essential hypertension, diabetes mellitus, end-stage renal disease, acute myocardial infarction, and coronary heart disease. It is likely that CF6 contributes to the pathogenesis of cardiovascular diseases, but further intensive investigation is needed.
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PMID:Coupling factor 6 as a novel vasoactive and proatherogenic peptide in vascular endothelial cells. 1948 38


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