cDNA Cloning of the Two Subunits of Phospholipase A2 Inhibitor PLIgamma from Blood Plasma of the Chinese Mamushi, Agkistrodon blomhoffii siniticus

Abstract

Three phospholipase A2 (PLA2) inhibitors (PLI) have been purified from the blood plasma of the Chinese mamushi, Agkistrodon blomhoffii siniticus; 1 of these, PLI gamma, contains 2 homologous subunits, PLI gamma‐A and PLI gamma‐B. The cDNAs encoding these 2 subunits of PLI gamma were isolated from a liver cDNA library by using fragments from polymerase chain reaction amplifications as probes and sequenced. The respective nucleotide sequences encoded 19‐residue signal sequences, followed by 181‐residue proteins. The calculated molecular masses were 20123 and 20150 Da for the PLI gamma‐A and PLI gamma‐B subunits, respectively; and PLI gamma‐A included a N‐linked carbohydrate site at Asn‐157. The sequences of these subunits contained 2 internal repeats of disulfide‐bonding pattern characteristic to those of urokinase‐type plasminogen activator receptor and members of the Ly‐6 superfamily. A phylogenetic analysis comparing the amino acid sequences of PLI gamma‐A and PLI gamma‐B with those for other snakes revealed that the gene duplication leading to these 2 subunits occurred before the divergence of Viperidae and Elapidae.