Chen X, Gross R W
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Biochemistry. 1995 Jun 6;34(22):7356-64. doi: 10.1021/bi00022a008.
The functional role of distinct phospholipid subclasses and molecular species in modulating gramicidin-mediated K+ flux was characterized through quantification of changes in the fluorescence intensity of ion specific fluorescent probes encapsulated inside vesicles comprised of individual molecular species of plasmenylcholine and phosphatidylcholine. The rate constant of gramicidin-mediated K+ ion flux across bilayers comprised of 1-O-(Z)-hexadec-1'-enyl-2-octadec-9'-enoyl-sn-glycero-3-p hos phocholine (plasmenylcholine) was 18.9 +/- 1.7 s-1, while that present across bilayers comprised of 1-hexadecanoyl-2-octadec-9'-enoyl-sn-glycero-3-phosphocholine (phosphatidylcholine) was 12.3 +/- 1.5 s-1. The observed changes were not due to alterations in the nature of the sn-2 aliphatic chain or the net surface charge present at the membrane interface and were unaltered by the addition of several amphiphilic agents (including charged amphiphiles), suggesting that the observed alterations specifically reflect changes in channel function which result from the covalent alteration of host phospholipid in the proximal portion of the sn-1 aliphatic chain (i.e., phospholipid subclass-specific alterations). Addition of cholesterol to bilayer matrices comprised of plasmenylcholine resulted in dose-dependent attenuation of the rate of gramicidin-mediated K+ flux, but did not alter the rate of gramicidin-mediated K+ flux in membranes comprised of phosphatidylcholine. Gramicidin ion channels experience distinct environments in membranes comprised of phosphatidylcholine and plasmenylcholine host lipids demonstrated by both the different fluorescence anisotropies of endogenous tryptophan residues and the different C=O stretching frequencies of intramonomer carbonyls in gramicidin incorporated into these two choline glycerophospholipid subclasses.(ABSTRACT TRUNCATED AT 250 WORDS)
通过对包裹在由缩醛磷脂酰胆碱和磷脂酰胆碱的单个分子种类组成的囊泡内的离子特异性荧光探针的荧光强度变化进行定量，表征了不同磷脂亚类和分子种类在调节短杆菌肽介导的钾离子通量中的功能作用。由1-O-(Z)-十六碳-1'-烯基-2-十八碳-9'-烯酰基-sn-甘油-3-磷酸胆碱（缩醛磷脂酰胆碱）组成的双层膜上，短杆菌肽介导的钾离子通量的速率常数为18.9±1.7 s⁻¹，而由1-十六烷酰基-2-十八碳-9'-烯酰基-sn-甘油-3-磷酸胆碱（磷脂酰胆碱）组成的双层膜上的速率常数为12.3±1.5 s⁻¹。观察到的变化并非由于sn-2脂肪链性质或膜界面处净表面电荷的改变，并且添加几种两亲剂（包括带电荷的两亲剂）后也未改变，这表明观察到的变化具体反映了通道功能的变化，该变化是由sn-1脂肪链近端宿主磷脂的共价改变引起的（即磷脂亚类特异性改变）。向由缩醛磷脂酰胆碱组成的双层膜基质中添加胆固醇会导致短杆菌肽介导的钾离子通量速率呈剂量依赖性衰减，但不会改变由磷脂酰胆碱组成的膜中短杆菌肽介导的钾离子通量速率。短杆菌肽离子通道在由磷脂酰胆碱和缩醛磷脂酰胆碱宿主脂质组成的膜中经历不同的环境，这通过内源性色氨酸残基的不同荧光各向异性以及掺入这两种胆碱甘油磷脂亚类中的短杆菌肽中单体羰基的不同C=O伸缩频率得以证明。（摘要截断于250字）
