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1.
2.
Mu-Chin Tzeng Ming Jhy Hseu Jun Hai Yang Richard John Guillory 《The protein journal》1986,5(3):221-228
Snake presynaptic toxins such as crotoxin, β-bungarotoxin and taipoxin block neuromuscular transmission through inhibiting the release of acetylcholine by their phospholipase A2 activities. On the other hand, many other phospholipase A2s show little neurotoxicity. It is likely that the difference lies in whether high affinity binding to nerve cell membranes exists or not. To test this idea, crotoxin, β-bungarotoxin and taipoxin were first radioactively labeled with Na(125I) without loss of their neurotoxicity. Using the radioactive toxins we have found that each of the three showed specific binding to synaptosomal membranes from guinea pig brain. In contrast, we could not detect specific binding of a non-neurotoxic pancreatic phospholipase A2. Crotoxin and taipoxin, but not β-bungarotoxin, also bound specifically to membrane preparation from other tissues. The binding of each toxin was not greatly affected by the other two toxins. The photoaffinity labeling technique has been used to obtain further information about the components which bind crotoxin. For this purpose, (125I) crotoxin was derivatized with N-hydroxysuccinimidyl-4-azidobenzoate. Autoradiographic analysis of the membranes following photoirradiation in the presence of the modified crotoxin revealed that an 85K dalton component was preferentially covalently conjugated with the crotoxin analogue in a specific manner. 相似文献
3.
Ming Jhy Hseu Richard John Guillory Mu-Chin Tzeng 《Journal of bioenergetics and biomembranes》1990,22(1):39-50
Crotoxin is a neurotoxic phospholipase A2 capable of blocking synaptic transmission by inhibiting the release of neurotransmitters. The photoaffinity labeling technique was used to identify the neural membrane molecules involved in the binding of crotoxin. A photoactivatable, radioactive derivative of crotoxin was synthesized by reacting crotoxin withN-hydroxysuccinimidyl-4-azidobenzoate and with Na[125I]. Photoirradiation of synaptosomes from guinea pig brains in the presence of the crotoxin derivative resulted in the formation of a major radioactive conjugate of 100,000 daltons as revealed by autoradiography of a sodium dodecyl sulfate-polyacrylamide gel electrophoretic pattern. Pretreatment of the synaptosomes with trypsin,Staphylococcus aureus protease, or papain prevented the formation of this conjugate. The conjugate was not detected when plasma membranes from several nonneural tissues replaced the brain synaptosomes. Unmodified crotoxin inhibited the formation of this adduct with an IC50 of about 10–8 M. Mojave toxin, caudoxin, notexin,Naja naja PLA, and taipoxin also inhibited adduct formation with different potencies, while -bungarotoxin and pancreatic PLA were ineffective. We concluded that an 85,000-dalton protein is the major component responsible for the binding of crotoxin to synaptosomal membranes.On leave from Department of Biochemistry and Biophysics, University of Hawaii School of Medicine, Honolulu, Hawaii. 相似文献
4.
Fed-batch culture of Bacillus thuringiensis in a modified airlift reactor has been developed by using adaptive control of glucose concentration in the reactor. The glucose concentration was estimated via a correlation equation between carbon dioxide production rate and glucose consumption rate. The estimated glucose concentration as the output variable was fed back to computer for calculation of substrate addition. The modified reactor was an airlift reactor with a net draft tube. The airlift reactor had high oxygen transfer rate and low shear stress which were important factors for production of thuringiensin. Fed-batch culture of Bacillus thuringiensis in the modified airlift reactor provided significant improvement of thuringiensin production. (c) 1995 John Wiley & Sons, Inc. 相似文献
5.
Further characterization of the binding of human recombinant interleukin 2 to heparin and identification of putative binding sites 总被引:1,自引:1,他引:1
We have previously provided compelling evidence that human recombinant
interleukin 2 (IL-2) binds to the sulfated polysaccharides heparin, highly
sulfated heparan sulfate and fucoidan. Here we show that IL-2 binding is
dependent on heparin chain length, but with fragments as small as 15-mers
retaining binding activity. The addition of exogenous heparin has no effect
on the in vitro biological activity of IL-2. In addition soluble IL-2
receptor alpha and beta polypeptides do not compete with heparin for the
binding of IL-2. IL-2 bound by heparin is still recognized by two IL-2
specific monoclonal antibodies, 3H9 and H2- 8, whose epitopes lie in the
amino terminal region. Murine IL-2 unlike its human counterpart fails to
bind to heparin. Human IL-2 analogs with single amino acid substitutions at
positions Lys43, Thr51, and Gln126 analogs no longer bind to heparin. By
contrast the Arg38Ala analog retains heparin full heparin binding activity.
These experimental findings together with molecular modeling studies
suggest two putative heparin binding sites on human IL-2, one involving
four basic residues, Lys48, Lys49, Lys54, and His55, and the other being a
discontinuous site comprising Lys43, Lys64, Arg81, and Arg83. Neither of
these two clusters is completely conserved in murine IL-2. Overall our data
suggest that the binding of human IL-2 to heparin and heparan sulfate does
not interfere with IL-2/IL-2 receptor interactions. Therefore, binding to
glycosaminoglycan may be a mechanism for retaining the cytokine in an
active form close to its site of secretion in the tissue, thus favoring a
paracrine role for IL-2.
相似文献
6.
7.
Kuan-Min Fang Chung-Shi Yang†‡ Synthia H. Sun§ Shun-Fen Tzeng 《Journal of neurochemistry》2009,111(5):1225-1237
Microglia, the CNS resident macrophages responsible for the clearance of degenerating cellular fragments, are essential to tissue remodeling and repair after CNS injury. ATP can be released in large amounts after CNS injury and may mediate microglial activity through the ionotropic P2X and the metabotropic P2Y receptors. This study indicates that exposure to a high concentration of ATP for 30 min rapidly induces changes of the microglial cytoskeleton, and significantly attenuates microglial phagocytosis. A pharmacological approach showed that ATP-induced inhibition of microglial phagocytotic activity was due to P2X7 R activation, rather than that of P2YR. Activation of P2X7 R by its agonist, 2'-3'- O -(4-benzoyl)benzoyl-ATP (BzATP), produced a Ca2+ -independent reduction in microglial phagocytotic activity. In addition, the knockdown of P2X7 R expression by lentiviral-mediated shRNA interference or the blockade of P2X7 R activation by the specific antagonists, oxidized ATP (oxATP) and brilliant blue G, has efficiently restored the phagocytotic activity of ATP and BzATP-treated microglia. Our results reveal that P2X7 R activation may induce the formation of a Ca2+ -independent signaling complex, which results in the reduction of microglial phagocytosis. This suggests that exposure to ATP for a short-term period may cause insufficient clearance of tissue debris by microglia through P2X7 R activation after CNS injury, and that blockade of this receptor may preserve the phagocytosis of microglia and facilitate CNS tissue repair. 相似文献
8.
Nguyen Thi Nha Trang Chao-Yang Lai Hsiao-Chi Tsai Yuan-Li Huang Shan-Chi Liu Chun-Hao Tsai Yi-Chin Fong Huey-En Tzeng Chih-Hsin Tang 《International journal of biological sciences》2023,19(2):412
Osteosarcoma is a highly mortal bone tumor, with a high metastatic potential, promoted in part by the enzyme procollagen-lysine 2-oxoglutarate 5-dioxygenase 2 (PLOD2). Increasing level of PLOD2 in osteosarcoma tissue correlates with lymphatic and distant metastasis. The adipokine apelin (APLN) is also found in different cancers and APLN upregulation promotes angiogenesis and metastasis, but its effects on osteosarcoma metastasis are uncertain. We explored APLN functioning in metastatic osteosarcoma. An analysis of records from the Gene Expression Omnibus (GEO) database showed higher levels of APLN expression in osteosarcoma tissue than in normal tissue. Similarly, levels of APLN and PLOD2 mRNA synthesis were upregulated in osteosarcoma tissue. Levels of APLN and PLOD2 protein correlated positively with osteosarcoma clinical stages. APLN increased PLOD2 expression in human osteosarcoma cell lines and cell migration via the mammalian Sterile 20-like kinase 1 (MST1), monopolar spindle-one-binder protein (MOB)1, and YAP cascades, and through hsa_circ_0000004 functioning as a sponge of miR-1303. We also found that knockdown of APLN antagonized lung metastasis in mice with osteosarcoma. APLN may be a therapeutic target in osteosarcoma metastasis. 相似文献
9.
Nguyen Nhung Nath Nandan Deseri Luca Tzeng Edith Velankar Sachin S. Pocivavsek Luka 《Biomechanics and modeling in mechanobiology》2020,19(6):2375-2395
Biomechanics and Modeling in Mechanobiology - Wrinkling is a ubiquitous surface phenomenon in many biological tissues and is believed to play an important role in arterial health. As arteries are... 相似文献
10.