ENTEROLOBIN: TOXIN AND WHAT ELSE?

SOUSA, M.V.(1), RICART, C.A.O. (1), FONTES, W. (1), LIMA, C.M.R. (1), MORHY, L. (1)

(1)Brazilian Center for Protein Research, Department of Cell Biology, University of Brasilia, Brasilia, DF, Brazil, 70910-900.

Enterolobin was described in the mid 80s as the first cytolytic plant protein. It was purified from Enterolobium contortisiliquum seeds, and was able to lyse red blood cells and other cell types. Its amino acid sequence and oligomerization pattern shared several similarities with aerolysins - pore-forming toxins from Aeromonas bacteria. Further biological characterization demonstrated that enterolobin possesses toxic activity against insect larvae and pro-inflammatory action in rats. The toxin was later shown to be localized in seed cell cytoplasm and nucleus, raising questions on its physiological role in the plant apart from a defensive one. Recent database searches using Double Twist engines found that enterolobin sequence has two high score pairs (HSPs) overlapping type III antifreeze protein signatures. Furthermore, preliminary data pointed to a probable protective function of enterolobin against hydric and saline stresses over the seed. Besides its toxicity to possible predators of E. contortisiliquum seeds, enterolobin may also carry a general anti-stress activity. In the field of biotechnological applications, some blood cells pose resistance to cytolysis by enterolobin, so that a patent request for a new and fast cell isolation process is being prepared for deposit. Enterolobin DNA cloning, sequencing and expressing are underway. Future site-directed mutagenesis studies associated with biological, biochemical and structural characterization of mutant enterolobins will shed brighter light on the mechanism of action, physiological functions and biotechnological applications of enterolobin.

Acknowledgements: CNPq, PADCT, FAPDF, FUB-UnB (Brazil) and IFS (Sweden) for facilities and financial support, students and collaborators.

CORRESPONDENCE TO:

SOUSA, M.V., Brazilian Center for Protein Research, Department of Cell Biology, University of Brasilia, Brasilia, DF, Brazil, 70910-900., Email: mvsousa@unb.br