CHARACTERIZATION OF THE ELONGATION-FACTORS FROM CALF BRAIN .3. PROPERTIES OF THE GTPASE ACTIVITY OF EF-1-ALPHA AND MODE OF ACTION OF KIRROMYCIN
CHARACTERIZATION OF THE ELONGATION-FACTORS FROM CALF BRAIN .3. PROPERTIES OF THE GTPASE ACTIVITY OF EF-1-ALPHA AND MODE OF ACTION OF KIRROMYCIN
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DOI：
10.1111/j.1432-1033.1986.tb10490.x
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发表时间：
1986-12-15
期刊：
影响因子：
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通讯作者：
PARMEGGIANI, A
中科院分区：
文献类型：
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作者：
CRECHET, JB;PARMEGGIANI, A
在不同实验条件下对牛脑EF-1α的GTP酶活性进行了研究，并与EF-Tu进行了比较。EF-1GTP在没有氨基酰-tRNA(AA-tRNA)和核糖体(固有的GTP活性)的情况下表现出比EF-Tu高得多的GTP酶转换率，这是由于结合的α和游离的GTP之间有更高的交换率。随着单价阳离子浓度的增加，EF-1α固有的GTP酶活性增强，K+比NH+4更有效。与EF-Tu不同，AA-tRNA比核糖体更能刺激EF-1αGTP酶的活性。然而，核糖体强烈地增强了AA-tRNA效应。在没有AA-tRNA的情况下，GTP酶周转的限速步骤似乎是GTP的水解，而在它的存在下，Gdp/GTP交换反应变得限速，因为EF-1β的加入提高了GTP周转GTP酶的活性。克洛霉素适度抑制EF-1α的内源性GTP酶；当AA-tRNA存在时，这种作用转化为刺激。核糖体的加入消除了克洛霉素的任何作用。在核糖体存在的情况下，克洛霉素不能影响EF-1α/鸟嘌呤核苷酸相互作用，这表明与EF-Tu不同，EF-1α·GdP/GTP交换反应发生在核糖体上。
The GTPase activity of purified EF‐1α from calf brain has been studied under various experimental conditions and compared with that of EF‐Tu. EF‐1α displays a much higher GTPase turnover than EF‐Tu in the absence of aminoacyl‐tRNA (aa‐tRNA) and ribosomes (intrinsic GTPase activity); this is due to the higher exchange rate between bound GDP and free GTP. Also the intrinsic GTPase of EF‐1α is enhanced by increasing the concentration of monovalent cations, K+being more effective than NH+4. Differently from EF‐Tu, aa‐tRNA is much more active than ribosomes in stimulating the EF‐1α GTPase activity. However, ribosomes strongly reinforce the aa‐tRNA effect. In the absence of aa‐tRNA the rate‐limiting step of the GTPase turnover appears to be the hydrolysis of GTP, whereas in its presence the GDP/GTP exchange reaction becomes rate‐limiting, since addition of EF‐1β enhances turnover GTPase activity. Kirromycin moderately inhibits the intrinsic GTPase of EF‐1α; this effect turns into stimulation when aa‐tRNA is present. Addition of ribosomes abolishes any kirromycin effect. The inability of kirromycin to affect the EF‐1α/guanine‐nucleotide interaction in the presence of ribosomes shows that, differently from EF‐Tu, the EF‐1α· GDP/GTP exchange reaction takes place on the ribosome.