Langlois R, Cantor C R, Vince R, Pestka S
Biochemistry. 1977 May 31;16(11):2349-56. doi: 10.1021/bi00630a007.
The effects of chloramphenical on the binding kinetics of a fluorescein isothiocyanate derivative of 9(S)-erythromycylamine with 70S and 50S ribosomes have been studied by direct fluorimetric measurements. While chloramphenicol had little effect on the second-order 70S binding rate of the erythromycin analogue, it substantially reduced the dissociation rate of the fluorescent antibiotic-70S ribosome complex. This could be explained by simultaneous binding of both antibiotics to the 70S ribosome. The kinetic results suggest that chloramphenicol-saturated 70S particles bind the erythromycin analogue four times stronger and this was confirmed by direct binding studies. In additon, chloramphenicol causes a twofold increase in the intrinsic fluorescence of the 70S-bound analogue. This increase in fluorescence was used to study the kinetics of chloramphenicol binding to 70S ribosomes containing the fluorescent derivative. The fluorescence change followed first-order kinetics, suggesting that chloramphenicol induces a conformational change in the 70S particle. This could explain both its effect on erythromycin binding and on the fluorescence of bound analogue. Less detailed results with the 50S particle indicate a qualitively similar picture of erythromycin-chloramphenicol interactions.
通过直接荧光测量研究了氯霉素对9(S)-红霉素胺的异硫氰酸荧光素衍生物与70S和50S核糖体结合动力学的影响。虽然氯霉素对红霉素类似物的二级70S结合速率影响很小，但它显著降低了荧光抗生素-70S核糖体复合物的解离速率。这可以通过两种抗生素同时结合到70S核糖体上来解释。动力学结果表明，氯霉素饱和的70S颗粒与红霉素类似物的结合力强四倍，这一点通过直接结合研究得到了证实。此外，氯霉素使结合在70S上的类似物的固有荧光增加了两倍。这种荧光增加被用于研究氯霉素与含有荧光衍生物的70S核糖体结合的动力学。荧光变化遵循一级动力学，表明氯霉素诱导70S颗粒发生构象变化。这可以解释其对红霉素结合和结合类似物荧光的影响。关于50S颗粒的不太详细的结果表明，红霉素-氯霉素相互作用的情况在性质上类似。
