Conformation and orientation of penetratin in phospholipid membranes.
The binding, conformation and orientation of a hydrophilic vector peptide penetratin in lipid membranes and its state of self-association in solution were examined using circular dichroism (CD), analytical ultracentrifugation and fluorescence spectroscopy. In aqueous solution, penetratin exhibited a low helicity and sedimented as a monomer in the concentration range approximately 50-500 microM. The partitioning of penetratin into phospholipid vesicles was determined using tryptophan fluorescence anisotropy titrations. The apparent penetratin affinity for 20% phosphatidylserine/80% egg phosphatidylcholine vesicles was inversely related to the total peptide concentration implying repulsive peptide-peptide interactions on the lipid surface. The circular dichroism spectra of the peptide when bound to unaligned 20% phosphatidylserine/80% egg phosphatidylcholine vesicles and aligned hydrated phospholipid multilayers were attributed to the presence of both alpha-helical and beta-turn structures. The orientation of the secondary structural elements was determined using oriented circular dichroism spectroscopy. From the known circular dichroism tensor components of the alpha-helix, it can be concluded that the orientation of the helical structures is predominantly perpendicular to the membrane surface, while that of the beta-type carbonyls is parallel to the membrane surface. On the basis of our observations, we propose a novel model for penetratin translocation.
Clayton
A H A
AH
Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, 3010, Victoria, Australia. andrew.clayton@ludwig.edu.au
Atcliffe
B W
BW
Howlett
G J
GJ
Sawyer
W H
WH
D002352:Carrier Proteins / Q000737:chemistry*; D057846:Cell-Penetrating Peptides; D008567:Membranes, Artificial; D010743:Phospholipids / Q000737:chemistry*; D011487:Protein Conformation
D002352:Carrier Proteins; D057846:Cell-Penetrating Peptides; D008567:Membranes, Artificial; D010743:Phospholipids; C414409:penetratin