Importance of Phosphatidylethanolamine for the Interaction of Apocytochrome c with Model Membranes Containing Phosphatidylserine

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• 作者：Taeho Ahn ; Doo-Byoung Oh ; Byoung-Chul Lee ; and Chul-Ho Yun
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：August 22, 2000
• 年：2000
• 卷：39
• 期：33
• 页码：10147 - 10153
• 全文大小：64K
• 年卷期：v.39,no.33(August 22, 2000)
• ISSN：1520-4995

文摘

The effect of phosphatidylethanolamine (PE) on the binding of apocytochrome c to modelmembranes was examined. When 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) of the standardvesicles composed of 80% of this lipid and 20% of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoserine (POPS)was gradually replaced with upward of 50% of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine(POPE), the binding increased appreciably. Ca²⁺, causing the phase separation of PS, also brought aboutincreased binding of apocytochrome c in the PC/PS system, underlining the importance of PS propertiesin membranes for the protein binding. The resonance energy transfer between Trp-59 in apocytochromec and pyrene-PS incorporated into bilayers showed that the replacement of PC with PE increased theextent of apocytochrome c penetration into membranes by a PE concentration-dependent manner. However,in the absence of PS, PE had no apparent effect on these functions of apocytochrome c, suggesting thatPE-induced change(s) of acidic membrane properties is important to the association of apocytochrome cwith vesicles. From the observations that the excimer to monomer fluorescence ratio of pyrene-PS increasedand the fluorescence of NBD-PS was quenched with increasing concentration of PE, it was deduced thatPE caused PS-enriched domains in PC/PE/PS membranes. The colocalization of pyrene-PS with BODIPY-PS by PE further supported the possibility. We suggest that PE-induced formation of PS-enriched domainsacts as binding sites for apocytochrome c in membranes.