Role of chirality in peptide-induced formation of cholesterol-rich domains.
The chiral specificity of the interactions of peptides that induce the formation of cholesterol-rich domains has not been extensively investigated. Both the peptide and most lipids are chiral, so there is a possibility that interactions between peptide and lipid could require chiral recognition. On the other hand, in our models with small peptides, the extent of folding of the peptide to form a specific binding pocket is limited. We have determined that replacing cholesterol with its enantiomer, ent-cholesterol, alters the modulation of lipid organization by peptides. The phase-transition properties of SOPC (1-stearoyl-2-oleoylphosphatidylcholine):cholesterol [in a 6:4 ratio with 0.2 mol% PtdIns(4,5)P2] are not significantly altered when ent-cholesterol replaces cholesterol. However, in the presence of 10 mol% of a 19-amino-acid, N-terminally myristoylated fragment (myristoyl-GGKLSKKKKGYNVNDEKAK-amide) of the protein NAP-22 (neuronal axonal membrane protein), the lipid mixture containing cholesterol undergoes separation into cholesterol-rich and cholesterol-depleted domains. This does not occur when ent-cholesterol replaces cholesterol. In another example, when N-acetyl-Leu-Trp-Tyr-Ile-Lys-amide (N-acetyl-LWYIK-amide) is added to SOPC:cholesterol (7:3 ratio), there is a marked increase in the transition enthalpy of the phospholipid, indicating separation of a cholesterol-depleted domain of SOPC. This phenomenon completely disappears when ent-cholesterol replaces cholesterol. The all-D-isomer of N-acetyl-LWYIK-amide also induces the formation of cholesterol-rich domains with natural cholesterol, but does so to a lesser extent with ent-cholesterol. Thus specific peptide chirality is not required for interaction with cholesterol-containing membranes. However, a specific chirality of membrane lipids is required for peptide-induced formation of cholesterol-rich domains.
Epand
Richard M
RM
Department of Biochemistry, McMaster University, 1200 Main Street West, Hamilton, Ontario, Canada L8N 3Z5. epand@mcmaster.ca
Rychnovsky
Scott D
SD
Belani
Jitendra D
JD
Epand
Raquel F
RF
D000595:Amino Acid Sequence; D002152:Calorimetry, Differential Scanning; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism*; D002942:Circular Dichroism; D021962:Membrane Microdomains / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism*; D019814:Myristic Acid / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry
D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D012097:Repressor Proteins; D019814:Myristic Acid; D002784:Cholesterol