Specificity of Loxosceles α clade phospholipase D enzymes for choline-containing lipids: Role of a conserved aromatic cage

PLoS Comput Biol. 2022 Feb 18;18(2):e1009871. doi: 10.1371/journal.pcbi.1009871. eCollection 2022 Feb.

Abstract

Spider venom GDPD-like phospholipases D (SicTox) have been identified to be one of the major toxins in recluse spider venom. They are divided into two major clades: the α clade and the β clade. Most α clade toxins present high activity against lipids with choline head groups such as sphingomyelin, while activities in β clade toxins vary and include preference for substrates containing ethanolamine headgroups (Sicarius terrosus, St_βIB1). A structural comparison of available structures of phospholipases D (PLDs) reveals a conserved aromatic cage in the α clade. To test the potential influence of the aromatic cage on membrane-lipid specificity we performed molecular dynamics (MD) simulations of the binding of several PLDs onto lipid bilayers containing choline headgroups; two SicTox from the α clade, Loxosceles intermedia αIA1 (Li_αIA) and Loxosceles laeta αIII1 (Ll_αIII1), and one from the β clade, St_βIB1. The simulation results reveal that the aromatic cage captures a choline-headgroup and suggest that the cage plays a major role in lipid specificity. We also simulated an engineered St_βIB1, where we introduced the aromatic cage, and this led to binding with choline-containing lipids. Moreover, a multiple sequence alignment revealed the conservation of the aromatic cage among the α clade PLDs. Here, we confirmed that the i-face of α and β clade PLDs is involved in their binding to choline and ethanolamine-containing bilayers, respectively. Furthermore, our results suggest a major role in choline lipid recognition of the aromatic cage of the α clade PLDs. The MD simulation results are supported by in vitro liposome binding assay experiments.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Choline
  • Ethanolamine
  • Phospholipase D* / metabolism
  • Phosphoric Diester Hydrolases / chemistry
  • Sphingomyelins
  • Spider Venoms* / chemistry
  • Spider Venoms* / metabolism

Substances

  • Sphingomyelins
  • Spider Venoms
  • Ethanolamine
  • Phosphoric Diester Hydrolases
  • Phospholipase D
  • Choline

Grants and funding

NR and EM acknowledge funding from the Research Council of Norway (Norges Forskningsråd, grants #251247 and #288008). MC acknowledges funding from the National Science Foundation (grant #1808716). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The Research Council of Norway: https://www.forskningsradet.no/ National Science Foundation, https://www.nsf.gov/.