Frederick Thomas E, Chebukati Janetricks N, Mair Chad E, Goff Philip C, Fanucci Gail E
Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA.
Biophys J. 2009 Mar 4;96(5):1847-55. doi: 10.1016/j.bpj.2008.12.3892.
Bis(monoacylglycero)phosphate (BMP) is an unusually shaped lipid found in relatively high percentage in the late endosome. Here, we report the characterization of the morphology and molecular organization of dioleoyl-BMP (DOBMP) with dynamic light scattering, transmission electron microscopy, nuclear magnetic resonance (NMR) spectroscopy, and electron paramagnetic resonance spectroscopy. The morphology of hydrated DOBMP dispersions varies with pH and ionic strength, and DOBMP vesicles are significantly smaller in diameter than phosphatidylcholine dispersions. At neutral pH, DOBMP forms highly structured, clustered dispersions 500 nm in size. On the other hand, at acidic pH, spherically shaped vesicles are formed. NMR and spin-labeled electron paramagnetic resonance demonstrate that DOBMP forms a lamellar mesophase with acyl-chain packing similar to that of other unsaturated phospholipids. (31)P NMR reveals an orientation of the phosphate group in DOBMP that differs significantly from that of other phospholipids. These macroscopic and microscopic structural characterizations suggest that the biosynthesis of BMP on the inner luminal membrane of maturing endosomes may possibly produce budded vesicles high in BMP content, which form small vesicular structures stabilized by the physical properties of the BMP lipid.
双（单酰甘油）磷酸酯（BMP）是一种形状异常的脂质，在内体晚期中所占比例相对较高。在此，我们报告了利用动态光散射、透射电子显微镜、核磁共振（NMR）光谱和电子顺磁共振光谱对二油酰-BMP（DOBMP）的形态和分子组织进行的表征。水合DOBMP分散体的形态随pH值和离子强度而变化，并且DOBMP囊泡的直径明显小于磷脂酰胆碱分散体。在中性pH值下，DOBMP形成高度结构化的、聚集的尺寸为500 nm的分散体。另一方面，在酸性pH值下，形成球形囊泡。NMR和自旋标记电子顺磁共振表明，DOBMP形成了一种层状中间相，其酰基链堆积与其他不饱和磷脂相似。磷-31 NMR揭示了DOBMP中磷酸基团的取向与其他磷脂有显著差异。这些宏观和微观结构表征表明，在成熟内体的内腔膜上BMP的生物合成可能会产生富含BMP的出芽囊泡，这些囊泡形成由BMP脂质的物理性质稳定的小泡状结构。
