Details

Autor(en) / Beteiligte

• Rafferty, Steven
• Luu, Betty
• March, Raymond E.
• Yee, Janet

Titel

Giardia lamblia encodes a functional flavohemoglobin

Ist Teil von

• Biochemical and biophysical research communications, 2010-08, Vol.399 (3), p.347-351

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2010

Quelle

MEDLINE

Beschreibungen/Notizen

• ► The parasitic protist Giardia lamblia encodes a functional flavohemoglobin. ► The enzyme likely protects Giardia from nitric oxide. ► Giardia has no known heme biosynthetic pathway and lacks other known heme proteins. ► Giardia heme acquisition and use is a new field opened by this work. Giardia lamblia is a pathogenic protist that infects the small intestine of mammals. As a facultative anaerobe, Giardia obtains all of its energy by substrate-level phosphorylation, lacks a functioning respiratory chain, and is not thought to require heme. However, sequencing of the G. lamblia genome has identified several putative heme proteins, one of which shares high sequence similarity to flavohemoglobins found in bacteria and some single-celled eukaryotes. We have cloned and characterized the functional properties of the G. lamblia flavohemoglobin. The protein is monomeric, binds heme and flavin adenine dinucleotide, and exhibits similar behavior to known flavohemoglobins, including NADH and NADPH oxidase activity, which is stimulated by addition of the nitric oxide donor DEA/NO. Based on its structural and functional properties, the likely role of this protein is to protect Giardia against oxygen, nitric oxide, or both. The presence of a Giardia gene encoding a functional heme protein raises questions on how this organism acquires the heme cofactor, which hitherto have been unexplored.