Flavohemoglobin and nitric oxide detoxification in the human protozoan parasite Giardia intestinalis |
| |
Authors: | Daniela Mastronicola Elena Forte Leopoldo Paolo Pucillo Alessandro Giuffrè |
| |
Institution: | a Department of Biochemical Sciences, CNR Institute of Molecular Biology and Pathology and Istituto Pasteur - Fondazione Cenci Bolognetti, Sapienza University of Rome, I-00185 Rome, Italy b Clinical Chemistry and Microbiology Laboratory, Istituto Nazionale per le Malattie Infettive I.R.C.C.S. ‘Lazzaro Spallanzani’, Rome, Italy |
| |
Abstract: | Flavohemoglobins (flavoHbs), commonly found in bacteria and fungi, afford protection from nitrosative stress by degrading nitric oxide (NO) to nitrate. Giardia intestinalis, a microaerophilic parasite causing one of the most common intestinal human infectious diseases worldwide, is the only pathogenic protozoon as yet identified coding for a flavoHb. By NO amperometry we show that, in the presence of NADH, the recombinant Giardia flavoHb metabolizes NO with high efficacy under aerobic conditions (TN = 116 ± 10 s−1 at 1 μM NO, T = 37 °C). The activity is O2]-dependent and characterized by an apparent KM,O2 = 22 ± 7 μM. Immunoblotting analysis shows that the protein is expressed at low levels in the vegetative trophozoites of Giardia; accordingly, these cells aerobically metabolize NO with low efficacy. Interestingly, in response to nitrosative stress (24-h incubation with ?5 mM nitrite) flavoHb expression is enhanced and the trophozoites thereby become able to metabolize NO efficiently, the activity being sensitive to both cyanide and carbon monoxide. The NO-donors S-nitrosoglutathione (GSNO) and DETA-NONOate mimicked the effect of nitrite on flavoHb expression. We propose that physiologically flavoHb contributes to NO detoxification in G. intestinalis. |
| |
Keywords: | flavoHb flavohemoglobin FDP flavodiiron protein NO nitric oxide NOS nitric oxide synthase PBS phosphate buffer saline EDTA ethylenediamine-tetracetic-acid sodium salt DETA-NONOate 3 3-bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene GSNO S-nitrosoglutathione |
本文献已被 ScienceDirect 等数据库收录! |
|