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Figure 2 | Molecular Brain

Figure 2

From: Directed evolution of a three-finger neurotoxin by using cDNA display yields antagonists as well as agonists of interleukin-6 receptor signaling

Figure 2

Sequence and structure comparison of MicTx3 with other three-finger proteins. (A) Sequence alignment of MicTx3 and representative three-finger proteins. Mature forms of MicTx3, erabutoxin A (Ebtx_A; UniProt Acc#P60775), α-cobratoxin (α-Cbtx; P01391), α-bungarotoxin (α-Bgtx, P60615) and mouse lynx1 (mLynx_1, Q9WVC2) were aligned by Clustal W method using the software, Lasergene ver.7 (DNASTAR, Madison, WI, USA). Conserved cysteine residues among the toxins are highlighted in green, and the disulfide bonds expected from analysis of α-Bgtx are shown by lines. The number of amino acid residues is shown on the right. (B) Superimposition of three-dimensional structures of the MicTx3 model and the α-Bgtx experimental structure. The three-dimensional model of MicTx3 was generated by the software, Internal Coordinate Mechanics (Molsoft, La Jolla, CA, USA), using the α-Bgtx structure (PDBID: 1ik8) as a modeling template. MicTx3 is shown in red and α-Bgtx is in blue. The numbers in Roman numerals represent the loop numbers. (C) Comparison of the MicTx3 model and the α-Bgtx experimental structure shown in (B). MicTx3 is shown in red and α-Bgtx is in blue. Disulfide bonds are colored green. In MicTx3, the loop sections highlighted in fluorescent green show the residues at the tips of the loops that were randomized in order to construct the library. (D) Schematic of the library based on the 3F scaffold. The anti-parallel β-sheets are depicted as blue arrows and the randomized loop residues are indicated as red crosses. Numbers such as Y24 and P11 indicate residues adjacent to the randomized residues (also see A). N and C indicate the amino- and carboxyl-terminals, respectively.

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