The presence of four iron-containing superoxide dismutase isozymes in Trypanosomatidae : characterization, subcellular localization, and phylogenetic origin in Trypanosoma brucei

Abstract

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B. V. for personal use, not for redistribution. The definitive version was published in Free Radical Biology and Medicine 40 (2006): 210-225, doi:10.1016/j.freeradbiomed.2005.06.021.Metalloenzymes such as the superoxide dismutases (SODs) form part of a defense mechanism that helps protect obligate and facultative aerobic organisms from oxygen toxicity and damage. Here, we report the presence in the trypanosomatid genomes of four SOD genes: soda, sodb1 and sodb2 and a newly identified sodc. All four genes of Trypanosoma brucei have been cloned (Tbsods), sequenced and overexpressed in Escherichia coli and shown to encode active dimeric FeSOD isozymes. Homology modelling of the structures of all four enzymes using available X-ray crystal structures of homologs showed that the four TbSOD structures were nearly identical. Subcellular localization using GFP-fusion proteins in procyclic insect trypomastigotes shows that TbSODB1 is mainly cytosolic, with a minor glycosomal component, TbSODB2 is mainly glycosomal with some activity in the cytosol and TbSODA and TbSODC are both mitochondrial isozymes. Phylogenetic studies of all available trypanosomatid SODs and 106 dimeric FeSODs and closely related cambialistic dimeric SOD sequences suggest that the trypanosomatid SODs have all been acquired by more than one event of horizontal gene transfer, followed by events of gene duplication.This work was supported by Interuniversity Attraction Pole programme of the Belgian Government P5/29 (to F.R.O.), the Institut National de la Santé et de la Recherche Médicale, the Institut Pasteur de Lille, and the Centre National de la Recherche Scientifique (to E.V.). F.D. was supported by a grant from the Ministère Français de l’Education Nationale, de la Recherche et de la Technologie. D.G. was supported by an ICP postdoctoral fellowship