Silva-Herzog E, Dreyfus G
Departamento de Genética Molecular, Instituto de Fisiología Celular, UNAM, Apdo. Postal 70-600, 04510, México D.F., Mexico.
Biochim Biophys Acta. 1999 May 18;1431(2):374-83. doi: 10.1016/s0167-4838(99)00058-8.
FliI is a key component of the flagellar export apparatus in Salmonella typhimurium. It catalyzes the hydrolysis of ATP which is necessary for flagellar assembly. Affinity blotting experiments showed that purified flagellin and hook protein, two flagellar axial proteins, interact specifically with FliI. The interaction of either of the two proteins with FliI, increases the intrinsic ATPase activity. The presence of either flagellin or hook protein stimulates ATPase activity in a specific and reversible manner. A Vmax of 0.12 nmol Pi min-1 microgram-1 and a Km for MgATP of 0.35 mM was determined for the unstimulated FliI; the presence of flagellin increased the Vmax to 0.35 nmol Pi min-1 microgram-1 and the Km for MgATP to 1.1 mM. The stimulation induced by the axial proteins was fully reversible suggesting a direct link between the catalytic activity of FliI and the export process.
FliI是鼠伤寒沙门氏菌鞭毛输出装置的关键组成部分。它催化ATP水解，这是鞭毛组装所必需的。亲和印迹实验表明，两种鞭毛轴向蛋白——纯化的鞭毛蛋白和钩蛋白——与FliI特异性相互作用。这两种蛋白中的任何一种与FliI相互作用，都会增加内在ATP酶活性。鞭毛蛋白或钩蛋白的存在以一种特异性且可逆的方式刺激ATP酶活性。未受刺激的FliI的Vmax为0.12 nmol Pi min-1 μg-1，MgATP的Km为0.35 mM；鞭毛蛋白的存在使Vmax增加到0.35 nmol Pi min-1 μg-1，MgATP的Km增加到1.1 mM。轴向蛋白诱导的刺激是完全可逆的，这表明FliI的催化活性与输出过程之间存在直接联系。
