Beschreibung:
<jats:p>The F‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ases (also called the F<jats:sub>1</jats:sub>F<jats:sub>o</jats:sub>‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ases or <jats:styled-content style="fixed-case">ATP</jats:styled-content> synthases) are multi‐subunit membrane‐bound molecular machines that produce <jats:styled-content style="fixed-case">ATP</jats:styled-content> in bacteria and in eukaryotic mitochondria and chloroplasts. The structures and enzymic mechanisms of their F<jats:sub>1</jats:sub>‐catalytic domains are highly conserved in all species investigated hitherto. However, there is evidence that the F‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ases from the group of protozoa known as Euglenozoa have novel features. Therefore, we have isolated pure and active F<jats:sub>1</jats:sub>‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ase from the euglenozoan parasite, <jats:italic>Trypanosoma brucei</jats:italic>, and characterized it. All of the usual eukaryotic subunits (α, β, γ, δ, and ε) were present in the enzyme, and, in addition, two unique features were detected. First, each of the three α‐subunits in the F<jats:sub>1</jats:sub>‐domain has been cleaved by proteolysis <jats:italic>in vivo</jats:italic> at two sites eight residues apart, producing two assembled fragments. Second, the <jats:italic>T. brucei</jats:italic> F<jats:sub>1</jats:sub>‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ase has an additional subunit, called p18, present in three copies per complex. Suppression of expression of p18 affected <jats:italic>in vitro</jats:italic> growth of both the insect and infectious mammalian forms of <jats:italic>T. brucei</jats:italic>. It also reduced the levels of monomeric and multimeric F‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ase complexes and diminished the <jats:italic>in vivo</jats:italic> hydrolytic activity of the enzyme significantly. These observations imply that p18 plays a role in the assembly of the F<jats:sub>1</jats:sub> domain. These unique features of the F<jats:sub>1</jats:sub>‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ase extend the list of special characteristics of the F‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ase from <jats:italic>T. brucei</jats:italic>, and also, demonstrate that the architecture of the F<jats:sub>1</jats:sub>‐<jats:styled-content style="fixed-case">ATP</jats:styled-content>ase complex is not strictly conserved in eukaryotes.</jats:p>