Mechanism of interaction of PITPalpha with membranes: conformational changes in the C-terminus associated with membrane binding.
Eukaryotic phosphatidylinositol transfer proteins (PITPs) are composed predominantly of small ( approximately 32 kDa) soluble proteins that bind and transfer a single phospholipid, normally phosphatidylinositol or phosphatidycholine. Two forms, PITPalpha and PITPbeta, which share approximately 80% amino acid sequence similarity, are known. Rat PITPalpha was labeled at specific single reactive Cys residues with I-AEDANS and used to examine PITP-membrane interactions. Upon binding to phospholipid vesicles, PITP labeled with AEDANS at the C-terminus, a region postulated to be involved in membrane binding, shows significant decreases in both steady-state and dynamic fluorescence anisotropy. In contrast, PITPs labeled with AEDANS at sites located distal to the C-terminus show increases in both steady-state and dynamic anisotropy. These results suggest that interaction of PITP with membrane surfaces leads to significant alterations in conformation and perhaps melting of the C-terminal helix.
Tremblay
Jacqueline M
JM
Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, 66160-7421, USA.
Unruh
Jay R
JR
Johnson
Carey K
CK
Yarbrough
Lynwood R
LR
D001665:Binding Sites; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry*; D008567:Membranes, Artificial; D049294:Phospholipid Transfer Proteins / Q000032:analysis* / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation
D008051:Lipid Bilayers; D008081:Liposomes; D008567:Membranes, Artificial; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids; C493468:Pitpn protein, mouse