3JR8

Crystal Structure of BthTX-II (Asp49-PLA2 from Bothrops jararacussu snake venom) with calcium ions

Summary for 3JR8

• Entry DOI: 10.2210/pdb3jr8/pdb
• Related: 1GMZ 2OQD
• Descriptor: Phospholipase A2 bothropstoxin-2, CALCIUM ION (3 entities in total)
• Functional Keywords: phospholipases a2, asp49-pla2, miotoxic asp49-pla2, bothropstoxin ii, bthtx-ii, disulfide bond, hydrolase, lipid degradation, metal-binding, secreted
• Biological source: Bothrops jararacussu
• Cellular location: Secreted: P45881
• Total number of polymer chains: 2
• Total formula weight: 28190.71

Authors

Borges, R.J.,dos Santos, J.I.,Fontes, M.R.M. (deposition date: 2009-09-08, release date: 2010-09-08, Last modification date: 2024-10-30)

Primary citation

dos Santos, J.I.,Cintra-Francischinelli, M.,Borges, R.J.,Fernandes, C.A.,Pizzo, P.,Cintra, A.C.,Braz, A.S.,Soares, A.M.,Fontes, M.R.
Structural, functional, and bioinformatics studies reveal a new snake venom homologue phospholipase A2 class.
Proteins, 79:61-78, 2011

PubMed Abstract: Phospholipases A₂ (PLA₂s) are enzymes responsible for membrane disruption through Ca(2+) -dependent hydrolysis of phospholipids. Lys49-PLA₂s are well-characterized homologue PLA₂s that do not show catalytic activity but can exert a pronounced local myotoxic effect. These homologue PLA₂s were first believed to present residual catalytic activity but experiments with a recombinant toxin show they are incapable of catalysis. Herein, we present a new homologue Asp49-PLA₂ (BthTX-II) that is also able to exert muscle damage. This toxin was isolated in 1992 and characterized as presenting very low catalytic activity. Interestingly, this myotoxic homologue Asp49-PLA₂ conserves all the residues responsible for Ca(2+) coordination and of the catalytic network, features thought to be fundamental for PLA₂ enzymatic activity. Previous crystallographic studies of apo BthTX-II suggested this toxin could be catalytically inactive since a distortion in the calcium binding loop was observed. In this article, we show BthTX-II is not catalytic based on an in vitro cell viability assay and time-lapse experiments on C2C12 myotube cell cultures, X-ray crystallography and phylogenetic studies. Cell culture experiments show that BthTX-II is devoid of catalytic activity, as already observed for Lys49-PLA₂s. Crystallographic studies of the complex BthTX-II/Ca(2+) show that the distortion of the calcium binding loop is still present and impairs ion coordination even though Ca(2+) are found interacting with other regions of the protein. Phylogenetic studies demonstrate that BthTX-II is more phylogenetically related to Lys49-PLA₂s than to other Asp49-PLA₂s, thus allowing Crotalinae subfamily PLA₂s to be classified into two main branches: a catalytic and a myotoxic one.

PubMed: 20878713
DOI: 10.1002/prot.22858

Experimental method

X-RAY DIFFRACTION (2.1 Å)