Huuskonen J, Olkkonen V M, Jauhiainen M, Metso J, Somerharju P, Ehnholm C
Department of Biochemistry, National Public Health Institute, Helsinki, Finland.
Biochim Biophys Acta. 1996 Oct 18;1303(3):207-14. doi: 10.1016/0005-2760(96)00103-8.
Phospholipid transfer protein (PLTP) is a plasma protein with two reported in vitro activities: transfer of phospholipids and modulation of HDL particle size. The mechanism of PLTP-mediated phospholipid transfer was studied by determining the acyl chain and headgroup specificity and comparing the results with those obtained with the non-specific lipid transfer protein (ns-LTP), a previously characterised intracellular transfer protein. To verify the results obtained with purified plasma PLTP, recombinant PLTP produced in COS-1 cells was used. The transfer rates were determined by monitoring the transfer of fluorescent, pyrene-labeled phospholipids from quenched donor phospholipid vesicles to HDL3 particles. When the length of the pyrene-labeled acyl chain was varied from 6 to 14 carbons, a fairly monotonous decrease in the transfer rate was observed. No difference in rate was observed for the isomers having the pyrene-labeled and unlabeled acyl chains in reversed positions. PLTP mediated equally the transfer of the various headgroup derivatives except phosphatidylethanolamine (PE), which was transferred 2-3-fold more slowly. In all experiments the plasma and recombinant PLTP behaved identically. The specificity patterns observed for PLTP and ns-LTP were very similar. No PLTP-phospholipid intermediate could be observed, indicating that PLTP, like ns-LTP, does not form a tight complex with the lipid substrate and may thus mediate the transfer of phospholipid via another, yet unspecified mechanism.
磷脂转运蛋白（PLTP）是一种血浆蛋白，具有两种已报道的体外活性：磷脂转运和高密度脂蛋白（HDL）颗粒大小调节。通过确定酰基链和头部基团特异性，并将结果与先前表征的细胞内转运蛋白非特异性脂质转运蛋白（ns-LTP）的结果进行比较，研究了PLTP介导的磷脂转运机制。为了验证用纯化的血浆PLTP获得的结果，使用了在COS-1细胞中产生的重组PLTP。通过监测荧光芘标记的磷脂从淬灭的供体磷脂囊泡到HDL3颗粒的转移来确定转移速率。当芘标记的酰基链长度从6个碳变化到14个碳时，观察到转移速率相当单调地下降。对于芘标记和未标记的酰基链位置相反的异构体，未观察到速率差异。除磷脂酰乙醇胺（PE）外，PLTP同样介导各种头部基团衍生物的转移，PE的转移速度慢2至3倍。在所有实验中，血浆和重组PLTP的行为相同。观察到的PLTP和ns-LTP的特异性模式非常相似。未观察到PLTP-磷脂中间体，这表明PLTP与ns-LTP一样，不会与脂质底物形成紧密复合物，因此可能通过另一种尚未明确的机制介导磷脂的转移。
