Molecular Cloning and Expression of a New A Chain of β

Molecular Cloning and
Expression of a New A Chain of β-Bungarotoxin

QIAN You-Cun, FAN Chun-Yang, LIU Xiao-Long¹, HU
Tai-Shan, YANG Sheng-Li and GONG Yi
( Shanghai Research Center of Biotechnology, CAS, Shanghai 200233,
China； ¹Shanghai Institute of Biochemistry, CAS,
Shanghai 200031,
China )

Abstract    The cDNA
encoding a new A chain of β-bungarotoxin was cloned from Bungarus
multicinctus. It encoded a 27－amino acid signal peptide and
a mature protein of 120 amino acids. The mature protein had the same 13
cysteines as the other A chains and shared high homology with them. The cDNA
encoding the PLA₂ from Naja naja atra was also cloned by
the use of the same degenerate primers. The cDNAs encoding the new A chain and
the PLA₂ were highly expressed in E. coli as soluble fusion
proteins and purified by affinity chromatography. The two recombinant proteins
achieved after digestion by Xa factor showed weak and strong PLA₂
activity, respectively.
Key Words    A chain of β-bungarotoxin； cDNA cloning； fusion expression； phospholipase A₂
activity

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