Acyl chain and headgroup specificity of human plasma phospholipid transfer protein.
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.
Department of Biochemistry, National Public Health Institute, Helsinki, Finland.
J
J
Huuskonen
V M
VM
Olkkonen
M
M
Jauhiainen
J
J
Metso
P
P
Somerharju
C
C
Ehnholm
D000818:Animals; D001692:Biological Transport; D019556:COS Cells; D002352:Carrier Proteins / Q000097:blood*; D002478:Cells, Cultured; D003001:Cloning, Molecular; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000097:blood*; D008081:Liposomes / Q000378:metabolism; D008565:Membrane Proteins / Q000097:blood*; D010316:Particle Size; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000737:chemistry* / Q000378:metabolism*; D011721:Pyrenes / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection; D014301:Trinitrobenzenes
D002352:Carrier Proteins; D005227:Fatty Acids; D008075:Lipoproteins, HDL; D008081:Liposomes; D008565:Membrane Proteins; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; D011721:Pyrenes; D011994:Recombinant Proteins; D014301:Trinitrobenzenes