The Calcium-Dependent Binding of Annexin V to Phospholipid Vesicles Influences the Bilayer Inner Fluidity Gradient

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• 作者：Francesco M. Megli ; Mariangela Selvaggi ; Susanne Liemann ; Ernesto Quagliariello ; and Robert Huber
• 刊名：Biochemistry
• 出版年：1998
• 出版时间：July 21, 1998
• 年：1998
• 卷：37
• 期：29
• 页码：10540 - 10546
• 全文大小：71K
• 年卷期：v.37,no.29(July 21, 1998)
• ISSN：1520-4995

文摘

The fluidity of the hydrophobic interior of phospholipid vesicles after calcium-dependent bindingof human annexin V (AVH) was studied using EPR spectroscopy. Vesicles (SUVs) composed of PC orPE and an acidic phospholipid (alternatively PS, PA, or CL) were probed at different bilayer depths byeither phosphatidylcholine, or the accompanying acidic phospholipid, bearing a spin label probe at positionC-5, C-12, or C-16 of the sn-2 acyl chain. Alternatively, the vesicle surface was probed with a polarhead spin labeled PE (PESL). The EPR spectra of annexin-bound bilayer domain(s) were obtained bycomputer spectral subtraction. The order parameter values (S) from the resulting difference spectra revealedthat the bilayer hydrophobic interior has a greatly altered fluidity gradient, with an increased rigidity upto the C-12 position. Thereafter, the rigidification progressively vanished. The effect is not linked to thephospholipid class, since all the acidic phospholipid spectra, as well as phosphatidylcholine, shared thesame sensitivity to the bound protein. The observed membrane rigidification appears to parallel the"crystallizing" tendency of vesicle-bound annexin V, but may not be involved in the calcium channelingactivity of this protein.