Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.6 (thromboplastin)
 13,278 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Botulinum neurotoxin type A (BoNT/A) selectively and irreversibly inhibits acetylcholine release from peripheral nerve endings. While the toxin's heavy (H) chain contributes to neuronal binding and internalization, its light (L) chain is a Zn(2+)-dependent endoprotease that intracellularly cleaves synaptosomal-associated protein of M(r) = 25 kDa (SNAP-25). For research and clinical exploitation of this uniquely-acting neurotoxin, recombinant wild-type L chain was produced together with a mutant in which His227 in the Zn(2+)-binding motif was substituted by Tyr. The PCR-amplified wild-type and mutant L chain genes were cloned, fused to the gene for maltose-binding protein, and expressed at high levels in Escherichia coli. The soluble fusion proteins were purified using amylose affinity chromatography, and, after factor Xa cleavage, the free L chains were isolated. The wild-type was shown to proteolyze SNAP-25 at a rate approaching that of the native chain while the mutant was inactive. Reconstitution of the pure wild-type L chain with native homogeneous H chain yielded a disulfide-linked dichain form that inhibited neuromuscular transmission in vitro and produced the symptoms of botulism in vivo. After reconstitution with the H chain, the Tyr227 mutant L chain failed to show any neuroparalytic activity in either of these assays. This methodology allows, for the first time, routine preparation of recombinant forms of the L chain that are needed to decipher the molecular details of its interaction with substrate and, thereby, assist the design of effective inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Expression and purification of the light chain of botulinum neurotoxin A: a single mutation abolishes its cleavage of SNAP-25 and neurotoxicity after reconstitution with the heavy chain. 757 32

Twenty-one healthy greyhounds with no history or clinical signs of bleeding disorders, and no abnormalities on physical examination, complete blood count, serum biochemistry profiles (in dogs more than five years of age), and SNAP-4DX test for vector borne diseases underwent routine gonadectomies at the Ohio State University Veterinary Teaching Hospital. Blood samples were collected 24 hours before and after surgery by jugular venepuncture for thromboelastography and haemostasis assays (prothrombin time [PT], activated partial thromboplastin time [aPTT], fibrinogen concentration). The magnitude of the bleeding in each patient was estimated using a bleeding scoring system recently validated in greyhounds. Eight dogs were classified as bleeders and 13 as non-bleeders. Thromboelastograph (TEG) tracings in bleeders were different to that of non-bleeders. Neither sex (odds ratio [OR]: 0.148, P=0.05), haematocrit (OR: 0.907, P=0.39), platelet count (OR: 0.996, P=0.65) or age (OR: 0.949, P=0.83) were predictors of the outcome. None of the variables that evaluated clot kinetics, and fibrinolysis (that is, aPTT OR: 0.781, P=0.51; PT OR: 1.337, P=0.63; TEG(R) OR: 1.269, P=0.06; TEG(K) OR: 1.696, P=0.05; TEG(LY60) OR: 1.028, P=0.81) were able to predict the bleeding episodes. Only the TEG variables that represent the fibrin cross-linking of the clot (TEG(angle) OR: 0.903, P=0.03); and the strength of the clot (TEG(MA) OR: 0.833, P=0.03) were considered predictors of the outcome.
 ...
PMID:Thromboelastographic changes after gonadectomy in retired racing greyhounds. 2172 53