Unexpected complexity of the ammonia monooxygenase in archaea.
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Archaeal AMO is an integral membrane complex catalysing the first, rate-limiting step of nitrification.
"step of nitrification is the oxidation of ammonia via the integral membrane protein complex ammonia monooxygenase (AMO)"
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Native membrane complexes of two AOA contain AmoA, AmoB, AmoC, AmoX and two new AOA-specific subunits, AmoY and AmoZ.
"Besides the known AmoABC subunits and the earlier predicted AmoX, two new protein subunits, AmoY and AmoZ, were identified."
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AmoA, AmoB and AmoC are among the most abundant proteins of the AOA membrane fraction.
"AMO subunits (AmoA, AmoB, and AmoC) were among the most abundant proteins (22% of iBAQ normalized intensity) detected overall in these membrane fractions."
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AOA have a single cell membrane and an S-layer that creates a pseudo-periplasm, toward which the AMO active site most likely faces.
"However, it is likely that the active site as well as the soluble AmoB and AmoZ domains are situated toward the pseudo-periplasmic space."
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No AMO structure (bacterial or archaeal) has been solved.
"no structural studies have been successfully carried out for any AMO complex, bacterial or archaeal"