Synthetic peptide-containing surfactants--evaluation of transmembrane versus amphipathic helices and surfactant protein C poly-valyl to poly-leucyl substitution.
Pulmonary surfactant contains two hydrophobic proteins, SP-B and SP-C. With the aim of identifying synthetic SP-B and SP-C substitutes for replacement therapy of respiratory distress syndromes, we have studied two transmembrane peptides and two amphipathic peptides that are located in the plane of a phospholipid bilayer. One amphipathic peptide was designed by changing the amino acid sequence, but not the composition or size, of the 21-residue peptide KL4. This peptide, designated KL(2,3) from its spacing of nonpolar and polar residues, exhibited similar alpha-helical content as KL4 but was oriented along a phospholipid bilayer plane, in contrast to the transmembrane orientation of KL4 in the same environment. The second amphipathic peptide analyzed was succinyl-LLEKLLEWLK-amide (WMAP10). KL4 more efficiently accelerated the spreading of a mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (Pam2GroPCho)/phosphatidylglycerol (PtdGro)/palmitic acid (PamOH), 68:22:9 (by mass), at an air/water interface than did any of the amphipathic peptides. Similarly, KL4, but not KL(2,3), when present in an interfacial monolayer composed of Pam2GroPCho/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol, 7:3 (by mass), increased lipid insertion from subphase vesicles. An SP-C analogue, SP-C(Leu), with all helical valyl residues in native SP-C replaced with Leu and the palmitoylcysteines at positions 5 and 6 replaced with Ser, but otherwise with essentially the same primary structure as the native peptide, was analyzed. SP-C(Leu) exhibited similar alpha-helical content as native SP-C and a transmembrane orientation and, in contrast to poly-valyl-containing synthetic peptides, it folds into a helical conformation after acid-induced denaturation. SP-C(Leu) accelerated the spreading of Pam2GroPCho/PtdGro/PamOH, 68:22:9 (by mass), almost identically to native SP-C, and lowered the surface tension during rapid cyclic film compressions in a pulsating bubble surfactometer to near zero and 43 mN/m at minimum and maximum bubble size, respectively. Airway instillation of 2% (by mass) SP-C(Leu) combined with Pam2GroPCho/PtdGro/PamOH in preterm rabbit fetuses improved dynamic lung compliance by about 30% compared with untreated controls.
Department of Clinical Chemistry, Karolinska Institutet at Karolinska and Danderyd Hospital, Sweden.
G
G
Nilsson
M
M
Gustafsson
G
G
Vandenbussche
E
E
Veldhuizen
W J
WJ
Griffiths
J
J
Sjövall
H P
HP
Haagsman
J M
JM
Ruysschaert
B
B
Robertson
T
T
Curstedt
J
J
Johansson
D000818:Animals; D000831:Animals, Newborn; D002942:Circular Dichroism; D005069:Evaluation Studies as Topic; D006801:Humans; D007231:Infant, Newborn; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins / Q000494:pharmacology*; D008958:Models, Molecular; D009842:Oligopeptides / Q000138:chemical synthesis / Q000494:pharmacology; D010455:Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D017433:Protein Structure, Secondary; D011506:Proteins; D011510:Proteolipids / Q000494:pharmacology*; D011663:Pulmonary Surfactants / Q000138:chemical synthesis / Q000494:pharmacology*; D011817:Rabbits; D011994:Recombinant Proteins; D012127:Respiratory Distress Syndrome, Newborn / Q000628:therapy; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship; D013501:Surface-Active Agents / Q000138:chemical synthesis / Q000494:pharmacology*
D036341:Intercellular Signaling Peptides and Proteins; C113803:KL2.3 peptide, synthetic; C097558:KL4 surfactant; D008565:Membrane Proteins; D009842:Oligopeptides; D010455:Peptides; D011506:Proteins; D011510:Proteolipids; D011663:Pulmonary Surfactants; D011994:Recombinant Proteins; D013501:Surface-Active Agents; C113802:WMAP10 protein, recombinant