The trypanosome alternative oxidase exists as a monomer in Trypanosoma brucei mitochondria.
The bloodstream forms of African trypanosomes solely depend on trypanosome alternative oxidase (TAO), for respiration. Similar to alternative oxidases (AOXs) found in plants and fungi, TAO is a membrane-bound diiron protein. Here, we investigated if TAO exists as a dimer like plant AOXs, or as a monomer like that of fungi. We have found that TAO forms a homo-dimer on a regular SDS-PAGE in the absence of any reducing agent and exists as a monomer under reducing condition. However, TAO does not form a dimer upon treatment of mitochondria with diamide. TAO was found as a higher molecular mass complex on a Blue-native gel after solubilization with digitonin. In the detergent soluble form, TAO activity was stimulated under reducing and inhibited under oxidizing condition. However, these conditions have no effect on the TAO activity in the mitochondria. Moreover, chemical cross-linking analysis revealed that TAO could not be cross-linked when present in the mitochondria. Together, it suggests that like certain other hydrophobic membrane proteins, TAO forms a dimer or oligomer when solubilized with detergents, and the TAO-dimer is SDS-resistant. However, it exists as a monomer in Trypanosoma brucei mitochondria.
Chaudhuri
Minu
M
Department of Microbiology, School of Medicine, Meharry Medical College, Nashville, TN, 37208, USA. mchaudhuri@mmc.edu
Ott
Robert Daniel
RD
Saha
Lipi
L
Williams
Shuntae
S
Hill
George C
GC
D000818:Animals; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism; D019163:Reducing Agents; D014346:Trypanosoma brucei brucei / Q000201:enzymology*; D000099188:Alternative Oxidase
D024101:Mitochondrial Proteins; D010088:Oxidoreductases; D010940:Plant Proteins; D015800:Protozoan Proteins; D019163:Reducing Agents; D000099188:Alternative Oxidase