Comparison of the primary structures, cytotoxicities, and affinities to phospholipids of five kinds of cytotoxins from the venom of Indian cobra, Naja naja

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• 作者：Mieko Suzuki-Matsubara^a ; ^{m.suzuki@nsc.nagoya-cu.ac.jp" class="auth_mail" title="E-mail the corresponding author} ; Senarath B.P. Athauda^b ; Yoshiyuki Suzuki^a ; Kazumi Matsubara^a ; ¹ ; Akihiko Moriyama^a
• 关键词：CTX ; cytotoxin ; PBS ; phosphate buffered saline ; PC ; phosphatidylcholine ; PS ; phosphatidylserine ; PE ; phosphatidylethanolanine ; PA ; phosphatidic acid ; SM ; sphingomyeline ; PE ; phosphatidylethanolamine ; dN ; number of nucleotide substitutions per nonsynonymous site ; dS ; number of nucleotide substitutions per synonymous site
• 刊名：Comparative Biochemistry and Physiology, Part C
• 出版年：2016
• 出版时间：January 2016
• 年：2016
• 卷：179
• 期：Complete
• 页码：158-164
• 全文大小：1436 K

文摘

The molecular mechanism underlying the hemolytic and cytolytic processes of cobra cytotoxins (CTXs) is not yet fully elucidated. To examine this, we analyzed the amino acid sequences, hemolytic and cytotoxic activities, and affinities to phospholipids of the five major CTXs purified from the venom of Indian cobra, Naja naja. CTX2, CTX7, and CTX8 belonged to S-type, and CTX9 and CTX10 to P-type. Comparisons of CTX7 with CTX8 and CTX9 with CTX10 revealed similar primary structures and hemolytic and cytolytic activities. CTX2, whose primary structure was rather different from the others, showed several times weaker hemolytic and cytolytic biological activities than the others. The comparison of CTX2 with CTX7 suggested the importance of Lys30 in loop II for the strong hemolytic and cytolytic activities of S-type CTXs. Cloning of 12 CTX cDNAs from the Naja naja venom cDNA library revealed that 18 out of 23 substitutions found in CTX cDNAs were nonsynonymous. This clearly indicated the accelerated evolution of CTX genes. Multiple sequence alignment of 51 kinds of CTX cDNAs and calculations of nonsynonymous and synonymous substitutions indicated that the codons coding the three loops' regions, which may interact with the hydrophobic tails of phospholipids, have undergone an accelerated evolution. In contrast, the codons coding for amino acid residues considered to participate in the recognition and binding of the hydrophilic head groups of phospholipids, eight Cys residues, and those likely stabilizing β core structure, were all conserved.