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Arch Biochem Biophys. 2015 May 1;573:92-9. doi: 10.1016/j.abb.2015.03.007. Epub 2015 Mar 16.

Allosteric regulation of the Plasmodium falciparum cysteine protease falcipain-2 by heme.

Author information

1
School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, 21941-902 Rio de Janeiro, RJ, Brazil; Instituto de Bioquímica Médica, Programa de Biologia Molecular e Biotecnologia, Federal University of Rio de Janeiro - UFRJ, Rio de Janeiro, Brazil.
2
Instituto de Biofísica Carlos Chagas Filho, Federal University of Rio de Janeiro - UFRJ, 21941-902 Rio de Janeiro, Brazil.
3
Instituto de Bioquímica Médica, Programa de Biologia Molecular e Biotecnologia, Federal University of Rio de Janeiro - UFRJ, Rio de Janeiro, Brazil; Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular (INCT-EM), Brazil.
4
Department of Medicine, San Francisco General Hospital, University of California, San Francisco, CA 94143, USA.
5
Instituto de Biofísica Carlos Chagas Filho, Federal University of Rio de Janeiro - UFRJ, 21941-902 Rio de Janeiro, Brazil; Laboratory for Macromolecules, DIMAV, Brazilian National Institute of Metrology, Quality and Technology - INMETRO, Av. N. Sa. das Graças, 50, Xerém, Duque de Caxias-RJ 25250-020, Rio de Janeiro, Brazil.
6
School of Pharmacy, Federal University of Rio de Janeiro - UFRJ, 21941-902 Rio de Janeiro, RJ, Brazil; Laboratory for Macromolecules, DIMAV, Brazilian National Institute of Metrology, Quality and Technology - INMETRO, Av. N. Sa. das Graças, 50, Xerém, Duque de Caxias-RJ 25250-020, Rio de Janeiro, Brazil; National Institute of Science and Technology for Structural Biology and Bioimaging (INBEB-INCT), Federal University of Rio de Janeiro, Rio de Janeiro 21941-590, Brazil. Electronic address: LML@UFRJ.BR.

Abstract

During the erythrocytic cycle of Plasmodium falciparum malaria parasites break down host hemoglobin, resulting in the release of free heme (ferriprotoporphyrin IX). Heme is a generator of free radicals that cause oxidative stress, but it is detoxified by crystallization into hemozoin inside the food vacuole. We evaluated the interaction of heme and heme analogues with falcipain-2, a P. falciparum food vacuole cysteine protease that plays a key role in hemoglobin digestion. Heme bound to falcipain-2 with a 1:1 stoichiometry, and heme inhibited falcipain-2 activity against both human hemoglobin and chromogenic peptide substrates through a noncompetitive-like mechanism. A series of porphyrin analogues was screened for inhibition of falcipain-2, demonstrating a minor contribution of iron to heme-falcipain-2 interaction, and revealing dependence on both propionic and vinyl groups for inhibition of falcipain-2 by heme. Docking and molecular dynamics simulation unveiled a novel, inducible heme-binding moiety in falcipain-2 adjacent to the catalytic site. Kinetic data suggested that the noncompetitive-like inhibition was substrate inhibition induced by heme. Collectively these data suggest that binding of heme to falcipain-2 may limit the accumulation of free heme in the parasite food vacuole, providing a means of heme detoxification in addition to crystallization into hemozoin.

KEYWORDS:

Allostery; Falcipain; Ferriprotoporphyrin IX; Heme; Malaria

PMID:
25791019
DOI:
10.1016/j.abb.2015.03.007
[Indexed for MEDLINE]

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