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SOLUTION STRUCTURE OF CARDIOTOXIN IV, NMR, 12 STRUCTURESSOLUTION STRUCTURE OF CARDIOTOXIN IV, NMR, 12 STRUCTURES
Structural highlights
Function3SA4_NAJAT Basic protein that bind to cell membrane and depolarizes cardiomyocytes. This cytotoxin also shows lytic activities, but 2-fold more important than that of CTX-A2. It binds to the integrin alpha-V/beta-3 with a moderate affinity. Inhibits protein kinase C. It may interact with sulfatides in the cell membrane, which induces pore formation and cell internalization and is responsible for cytotoxicity in cardiomyocytes. It also may target the mitochondrial membrane and induces mitochondrial swelling and fragmentation.[1] [2] [3] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedCardiotoxin analogues IV (CTX IV) and II (CTX II) isolated from the venom of Taiwan Cobra (Naja naja atra) differ in their amino acid sequence by a single amino acid at the N-terminal end. Leucine at the N-terminal end in CTX II is replaced by arginine in CTX IV. CTX IV is an unique snake venom cardiotoxin as it is the only cardiotoxin isoform known so far which possesses a positively charged residue at the N-terminal amino acid. All other cardiotoxins have a hydrophobic amino acid (leucine or isoleucine) at their N-terminal end. The aim of the present study is to understand the effect(s) of the presence of a cationic residue on the structure and functional properties of cardiotoxin(s). Comparison of the hemolytic activities of CTX IV and CTX II shows that lytic activity of the former is at least twice as that shown by the latter. Comparison of the solution structures of CTX IV and CTX II using two-dimensional NMR spectroscopy and dynamical simulated annealing technique reveals that the backbone fold of both the toxin isoforms is almost similar. The secondary structural elements in these two cardiotoxin isoforms consist of long, triple-stranded, as well as short, double-stranded, antiparallel beta-sheets. Thermal denaturation experiments showed that the structure of CTX IV is more stable than that of CTX II. Critical analysis of the three-dimensional structures of CTX IV and CTX II reveals the presence of a "cationic" cluster comprising of positively charged residues on the concave side of the CTX IV molecule. Similar clusters consisting of positively charged residues are not found in CTX II. The differential erythrocyte lytic activities of these two cardiotoxins are attributed to the difference(s) in the distribution of the positively charged residues in their three-dimensional structures. Comparison of the hemolytic activity and solution structures of two snake venom cardiotoxin analogues which only differ in their N-terminal amino acid.,Jang JY, Krishnaswamy T, Kumar S, Jayaraman G, Yang PW, Yu C Biochemistry. 1997 Dec 2;36(48):14635-41. PMID:9398182[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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