Domain formation in phosphatidylcholine bilayers containing transmembrane peptides: specific effects of flanking residues.
Lateral segregation in biological membranes leads to the formation of domains. We have studied the lateral segregation in gel-state model membranes consisting of supported dipalmitoylphosphatidylcholine (DPPC) bilayers with various model peptides, using atomic force microscopy (AFM). The model peptides are derivatives of the Ac-GWWL(AL)(n)WWA-Etn peptides (the so-called WALP peptides) and have instead of tryptophans, other flanking residues. In a previous study, we found that WALP peptides induce the formation of extremely ordered, striated domains in supported DPPC bilayers. In this study, we show that WALP analogues with other uncharged residues (tyrosine, phenylalanine, or histidine at pH 9) can also induce the formation of striated domains, albeit in some cases with a slightly different pattern. The WALP analogues with positively charged residues (lysine or histidine at low pH) cannot induce striated domains and give rise to a completely different morphology: they induce irregularly shaped depressions in DPPC bilayers. The latter morphology is explained by the fact that the positively charged peptides repel each other and hence are not able to form striated domains in which they would have to be in close vicinity. They would reside in disordered, fluidlike lipid areas, appearing below the level of the ordered gel-state lipid domains, which would account for the irregularly shaped depressions.
Rinia
Hilde A
HA
Institute of Biomembranes, CBLE, Department Biochemistry of Membranes, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands. hilde.rinia@physik.uni-muenchen.de
Boots
Jan-Willem P
JW
Rijkers
Dirk T S
DT
Kik
Richard A
RA
Snel
Margot M E
MM
Demel
Rudy A
RA
Killian
J Antoinette
JA
van der Eerden
Jan P J M
JP
de Kruijff
Ben
B
D000595:Amino Acid Sequence; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D005614:Freeze Fracturing; D008051:Lipid Bilayers; D018625:Microscopy, Atomic Force; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010713:Phosphatidylcholines / Q000737:chemistry*
D008051:Lipid Bilayers; D010713:Phosphatidylcholines