title: Characterization of novel M-superfamily conotoxins with new disulfide linkage.
abstract: The M-superfamily with the typical Cys framework (-CC-C-C-CC-) is one of the seven major superfamilies of conotoxins found in the venom of cone snails. Based on the number of residues in the last Cys loop (between C4 and C5), M-superfamily conotoxins can be provisionally categorized into four branches (M-1, M-2, M-3, M-4) [Corpuz GP, Jacobsen RB, Jimenez EC, Watkins M, Walker C, Colledge C, Garrett JE, McDougal O, Li W, Gray WR, et al. (2005) Biochemistry44, 8176-8186]. Here we report the purification of seven M-superfamily conotoxins from Conus marmoreus (five are novel and two are known as mr3a and mr3b) and one known M-1 toxin tx3a from Conus textile. In addition, six novel cDNA sequences of M-superfamily conotoxins have been identified from C. marmoreus, Conus leopardus and Conus quercinus. Most of the above novel conotoxins belong to M-1 and M-2 and only one to M-3. The disulfide analyses of two M-1 conotoxins, mr3e and tx3a, revealed that they possess a new disulfide bond arrangement (C1-C5, C2-C4, C3-C6) which is different from those of the M-4 branch (C1-C4, C2-C5, C3-C6) and M-2 branch (C1-C6, C2-C4, C3-C5). This newly characterized disulfide connectivity was confirmed by comparing the HPLC profiles of native mr3e and its two regioselectively folded isoforms. This is the first report of three different patterns of disulfide connectivity in conotoxins with the same cysteine framework.
authors.affiliation: Key Laboratory of Proteomics, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Graduate School of the Chinese Academy of Sciences, 320 YueYang Road, Shanghai 200031, China.
authors.forename: Yu-Hong
authors.initials: YH
authors.lastname: Han
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Jiang
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Cai
authors.initials: C
authors.lastname: Xiao
authors.forename: Duo-Duo
authors.initials: DD
authors.lastname: Yuan
authors.forename: Xiao-Xia
authors.initials: XX
authors.lastname: Shao
authors.forename: Qiu-Yun
authors.initials: QY
authors.lastname: Dai
authors.forename: Ji-Sheng
authors.initials: JS
authors.lastname: Cheng
authors.forename: Cheng-Wu
authors.initials: CW
authors.lastname: Chi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D020916:Conotoxins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*; D052078:Conus Snail / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004220:Disulfides / Q000737:chemistry*; D008969:Molecular Sequence Data; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification
chemical_list: D020916:Conotoxins; D018076:DNA, Complementary; D004220:Disulfides; D020033:Protein Isoforms; D003545:Cysteine