Primary Structure of an Inactive Mutant of Phospholipase A2 in the Venom of Bungarus fasciatus (Banded krait)1

Abstract

From the acidic components of Bungarus fasciatus venom, a very small amount (0.16%) of a novel phospholipase A2 was obtained. Both neurotoxicity and enzyme activity were found to be lacking. Amino acid sequence study showed that it has a normal backbone of group I snake venom phospholipase A2 with 118 amino acid residues. The lack of enzyme activity was attributed to its mutation of the indispensable Asp residue to an Ala residue, i.e., the usual His-Asp47 turned out to be His-Ala47. This is the eighth isoform of phospholipase A2 found from the venom of Bungarus fasciatus. Examination of structural homology with three other isoforms revealed 66% similarity at most.

Sequences, geographic variations and molecular phylogeny of venom phospholipases and threefinger toxins of eastern India Bungarus fasciatus and kinetic analyses of its Pro31 phospholipases A2

“…All these venom proteins showed a single mass peak by ESI‐MS spectrometry, except that the PLA KBf‐II contained a substantial amount of the oxidized form (13 019 Da) besides the native form (13 003 Da). The KBf‐PLAs were also matched with previously reported PLA variants of the pooled Bf venom [3–6]; only one of them was found to be identical to Vb‐2, with the others being 94% similar to the other five Bf PLA isoforms (Fig. 3).…”

“…besides the native form (13 003 Da). The KBf-PLAs were also matched with previously reported PLA variants of the pooled Bf venom [3][4][5][6]; only one of them was found to be identical to Vb-2, with the others being 94% similar to the other five Bf PLA isoforms ( Fig. 3).…”

“…3). Apparently, only one of the KBf PLAs is identical to the previously reported Vb‐2, while the other five are ∼94–98% identical to Bf Va, Vb‐1, VI, XI‐2 (or X‐1) [3,5,10] and PL‐II (from Chinese Bf, accession number ), respectively. Although its cDNA has been cloned, KBf‐X is not expressed in both KBf venoms.…”

“…3). Two inactive PLA homologs, with N-terminal sequence either identical to Bf Ala49-PLA [5] or with a single substitution Val3ILe, were purified from both KBf venoms. The differences in their molecular masses (Table 1) and HPLC elution time ( Fig.…”

“…In the past, more than 20 proteins were purified and sequenced from pooled venom of Bungarus fasciatus (Bf), which was obtained from either the Miami Serpentarium Laboratory or south‐eastern Asia. The proteins include eight variants of phospholipases A 2 (EC3.1.1.4, PLAs) [3–6], four isoforms of threefinger toxins (3FTx) [7–10], at least one Kunitz protease inhibitors [10–12], a factor‐X activator [13], an acetylcholine esterase [14] and other enzymes [15]. The numbers of isoforms for PLA and 3FTx from the pooled Bf venom were high, but the intraspecies or the geographic variations of this venom species have not been explored.…”