HAMLET Forms Annular Oligomers When Deposited with Phospholipid Monolayers

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• 作者：Anne Baumann¹ ; ^&dagger ; ; Anja Underhaug Gjerde¹ ; ^&dagger ; ; Ming Ying¹ ; Catharina Svanborg² ; ³ ; Holm Holmsen¹ ; Wilhelm R. Glomm⁴ ; Aurora Martinez¹ ; ^{aurora.martinez@biomed.uib.no} ; &Oslash ; yvind Halskau¹ ; ⁵ ; ^{oyvind.halskau@mbi.uib.no}
• 关键词：AFM ; atomic force microscopy ; ANTS ; 8-aminonaphtalene-1 ; 3 ; 6-trisulfonic acid ; AO ; annular oligomer ; 伪-La ; 伪-lactalbumin ; BLA ; bovine 伪-lactalbumin ; DPX ; p-xyelene-bis-N-pyrimidium bromide ; HAMLET ; human 伪-lactalbumin made lethal to tumor cells ; LUV ; l
• 刊名：Journal of Molecular Biology
• 出版年：2012
• 期刊代码：102_00222836
• 类别：imm
• 出版时间：20 April, 2012
• 卷：418
• 期：1-2
• 页码：90-102
• 文件大小：1384 K

摘要

Recently, the anticancer activity of human 伪-lactalbumin made lethal to tumor cells (HAMLET) has been linked to its increased membrane affinity in vitro, at neutral pH, and ability to cause leakage relative to the inactive native bovine 伪-lactalbumin (BLA) protein. In this study, atomic force microscopy resolved membrane distortions and annular oligomers (AOs) produced by HAMLET when deposited at neutral pH on mica together with a negatively charged lipid monolayer. BLA, BAMLET (HAMLET's bovine counterpart) and membrane-binding Peptide C, corresponding to BLA residues 75-100, also form AO-like structures under these conditions but at higher subphase concentrations than HAMLET. The N-terminal Peptide A, which binds to membranes at acidic but not at neutral pH, did not form AOs. This suggests a correlation between the capacity of the proteins/peptides to integrate into the membrane at neutral pH鈥攁s observed by liposome content leakage and circular dichroism experiments鈥攁nd the formation of AOs, albeit at higher concentrations. Formation of AOs, which might be important to HAMLET's tumor toxic action, appears related to the increased tendency of the protein to populate intermediately folded states compared to the native protein, the formation of which is promoted by, but not uniquely dependent on, the oleic acid molecules associated with HAMLET.