Witzke N M, Bittman R
Biochemistry. 1984 Apr 10;23(8):1668-74. doi: 10.1021/bi00303a014.
The interactions of sonicated vesicles with the polyene antibiotics amphotericin B, candicidin, mediocidin , and a water-soluble, guanidine derivative of amphotericin B were examined by UV-visible spectroscopy at concentrations below which the polyenes become self-associated. The association constants, Kapp, and the numbers of binding sites per sterol or phospholipid molecule (n) were determined at 30 degrees C and pH 7.4. A single class of binding sites was found, with no evidence of cooperativity. For the binding of mediocidin , amphotericin B, and the guanidine derivative with phosphatidylcholine (PC), PC/cholesterol, and PC/ergosterol vesicles, Kapp was in the range of (1.0-3.0) X 10(6) M-1; Kapp was higher for candicidin-vesicle interaction, reaching 9.0 X 10(6) M-1 with PC/ergosterol vesicles. Binding of the guanidine derivative of amphotericin B to PC vesicles lacking sterol was extensive (n = 0.46); since the other polyenes, which have low aqueous solubilities, had n less than 0.05, positive charges in the mycosamine moiety appear to enhance the extent of polyene antibiotic interaction with the glycerophospholipid head group. Higher values of n (and, therefore, of nKapp ) were found with sterol-containing than with sterol-free vesicles, suggestive of penetration of the polyenes toward the interior of the bilayer when sterol is present. For binding to PC/sterol vesicles, nKapp followed the order of candicidin greater than guanidine derivative of amphotericin B greater than amphotericin B much greater than mediocidin . The values of n and nKapp were appreciably higher for amphotericin B-ergosterol than for amphotericin B-cholesterol interaction in vesicles.(ABSTRACT TRUNCATED AT 250 WORDS)
在低于多烯类抗生素自身缔合浓度的情况下，通过紫外可见光谱法研究了超声处理的囊泡与多烯抗生素两性霉素B、杀假丝菌素、间霉素以及两性霉素B的水溶性胍衍生物之间的相互作用。在30℃和pH 7.4条件下测定了缔合常数Kapp以及每个固醇或磷脂分子的结合位点数(n)。发现存在单一类别的结合位点，没有协同作用的证据。对于间霉素、两性霉素B以及胍衍生物与磷脂酰胆碱(PC)、PC/胆固醇和PC/麦角固醇囊泡的结合，Kapp在(1.0 - 3.0)×10⁶ M⁻¹范围内；杀假丝菌素与囊泡相互作用的Kapp较高，与PC/麦角固醇囊泡相互作用时达到9.0×10⁶ M⁻¹。两性霉素B的胍衍生物与不含固醇的PC囊泡的结合广泛(n = 0.46)；由于其他水溶性低的多烯类抗生素的n小于0.05，霉菌胺部分的正电荷似乎增强了多烯抗生素与甘油磷脂头部基团的相互作用程度。与不含固醇的囊泡相比，含固醇囊泡的n(以及nKapp)值更高，这表明当存在固醇时多烯类抗生素向双层内部渗透。对于与PC/固醇囊泡的结合，nKapp的顺序为杀假丝菌素＞两性霉素B的胍衍生物＞两性霉素B＞间霉素。在囊泡中，两性霉素B - 麦角固醇相互作用的n和nKapp值比两性霉素B - 胆固醇相互作用的明显更高。(摘要截短于250字)
