Separation and properties of the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus
Separation and properties of the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus
复制标题
黄色粘球菌营养细胞的细胞质和外膜的分离和性质
作者：
P. Orndorff;M. Dworkin
我们开发了分离黄色粘球菌营养细胞的细胞质和外膜的方法。用等密度离心法将乙二胺四乙酸-溶菌酶处理的细胞膜总组分分离为三个主要组分。琥珀酸脱氢酶和氰化物敏感的烟酰胺腺嘌呤二核苷酸氧化酶活性在第一组分(Rho=1.221 g/ml)和膜结合的2-酮-3-脱氧辛酸(Rho=1.166 g/ml)组分中分别占85%到90%和80%。中间(II)组分(Rho=1.185 g/ml)似乎是杂化膜组分，含有大约10%~20%的酶标记物和2-酮-3-脱氧辛酸。三个分离组份中均未检测到明显的脱氧核糖核酸或核糖核酸，但从总的膜组分中回收了26%的细胞脱氧核糖核酸和3%的总核糖核酸。磷脂酰乙醇胺占膜组分中磷脂的体积(60%~70%)。然而，几乎所有的磷脂酰丝氨酸和心磷脂都存在于组分I中，组分III似乎含有大量的溶血磷脂，与组分I相比，组分III的总磷脂含量几乎是组分I的3倍。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳法在总膜组份中分离了约40种多肽。其中2/3的多肽富含组份I，其余的富含组份III。组份II的带型与全膜组份相似。电子显微镜显示，黄色分枝杆菌的营养细胞具有与其他革兰氏阴性细菌相似的包膜，但分离的膜的泡状外观与报道的大肠杆菌和鼠伤寒沙门氏菌有所不同。从黄曲霉外膜磷脂含量高的角度讨论了黄曲霉外膜非典型的低密度问题。
We have developed methods for separating the cytoplasmic and outer membranes of vegetative cells of Myxococcus xanthus. The total membrane fraction from ethylenediaminetetraacetic acid-lysozyme-treated cells was resolved into three major fractions by isopycnic density centrifugation. Between 85 and 90% of the succinate dehydrogenase and cyanide-sensitive reduced nicotinamide adenine dinucleotide oxidase activity was found in the first (I) fraction (rho = 1.221 g/ml) and 80% of the membrane-associated 2-keto-3-deoxyoctonate was found in the third (III) fraction (rho = 1.166 g/ml). The middle (II) fraction (rho = 1.185 g/ml) appeared to be a hybrid membrane fraction and contained roughly 10 to 20% of the activity of the enzyme markers and 2-keto-3-deoxyoctonate. No significant amounts of deoxyribonucleic acid or ribonucleic acid were present in the three isolated fractions, although 26% of the total cellular deoxyribonucleic acid and 3% of the total ribonucleic acid were recovered with the total membrane fraction. Phosphatidylethanolamine made up the bulk (60 to 70%) of the phospholipids in the membrane fractions. However, virtually all of the phosphatidylserine and cardiolipin were found in fraction I. Fraction III appeared to contain elevated amounts of lysophospholipids and contained almost three times the amount of total phospholipid as compared with fraction I. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis resolved approximately 40 polypeptides in the total membrane fraction. Two-thirds of these polypeptides were enriched in fraction I, and the remainder was enriched in fraction III. Fraction II contained a banding pattern similar to the total membrane fraction. Electron microscopy revealed that vegetative cells of M. xanthus possessed an envelope similar to that of other gram-negative bacteria; however, the vesicular appearance of the isolated membranes was somewhat different from those reported for Escherichia coli and Salmonella typhimurium. The atypically low bouyant density of the outer membrane of M. xanthus is discussed with regard to the high phospholipid content of the outer membrane.