The Surfactant Peptide KL4 Sequence Is Inserted with a Transmembrane Orientation into the Endoplasmic Reticulum Membrane (original) (raw)
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Peptide-based synthetic pulmonary surfactant for the treatment of respiratory distress disorders
Current Opinion in Chemical Biology, 2016
KL 4 (Sinapultide) represents the first peptide-based replacement for surfactant protein B in pulmonary surfactant (PS) therapies approved for clinical use. Surfaxin, its formulation with PS lipids, shows the promise of synthetic PS for replacing animal-derived PS in the treatment of respiratory distress syndromes and for treating acute lung injury. Efforts to characterize the molecular basis for KL 4 function have revealed the peptide exhibits a helical structure which differentially partitions in response to both lipid saturation levels and pH. The penta-residue repeat of KL 4 leads to adaptive peptide helicity, varying with partitioning depth, and suggests structural plasticity may represent an important mechanism for differential trafficking of lipids, particularly in intra-alveolar surfactant for the formation of stable DPPC monolayers at air-water interfaces.
Simple, helical peptoid analogs of lung surfactant protein B
Chemistry & biology, 2005
interface, (2) the ability to reach near-zero surface tension upon film compression, and (3) the ability to reand Annelise E. Barron* spread upon multiple compressions and expansions of Department of Chemical and Biological Engineering surface area with minimal loss of surfactant into the Northwestern University subphase [10]. LS is composed of w90% lipids and 2145 Sheridan Road w10% surfactant proteins [5, 11-15]. The hydrophobic Evanston, Illinois 60208 surfactant proteins, SP-B and SP-C, in particular are essential to the proper biophysical function of LS for breathing and are thought to be involved in the organ-Summary ization and fluidization of the lipid film [10]. Films of the main lipid component of LS, dipalmitoyl The helical, amphipathic surfactant protein, SP-B, is phosphatidylcholine (DPPC), can reach near-zero sura critical element of pulmonary surfactant and hence face tension upon compression in vitro; however, this is an important therapeutic molecule. However, it is molecule is slow to adsorb to the interface and exhibits difficult to isolate from natural sources in high purity. poor respreadability [10]. With the addition of palmitoyl-We have created and studied three different, nonnatuoleoyl phosphatidylglycerol (POPG) and/or palmitic ral analogs of a bioactive SP-B fragment (SP-B 1-25 ), acid (PA), there is an increased rate of surfactant adusing oligo-N-substituted glycines (peptoids) with sorption and better respreadability than with DPPC simple, repetitive sequences designed to favor the alone [16]. However, these lipid mixtures do not reach formation of amphiphilic helices. For comparison, a sufficiently low surface tensions [16]
Functional importance of the NH2-terminal insertion sequence of lung surfactant protein B
AJP: Lung Cellular and Molecular Physiology, 2010
Lung surfactant protein B (SP-B) is required for proper surface activity of pulmonary surfactant. In model lung surfactant lipid systems composed of saturated and unsaturated lipids, the unsaturated lipids are removed from the film at high compression. It is thought that SP-B helps anchor these lipids closely to the monolayer in three-dimensional cylindrical structures termed "nanosilos" seen by atomic force microscopy imaging of deposited monolayers at high surface pressures. Here we explore the role of the SP-B NH2 terminus in the formation and stability of these cylindrical structures, specifically the distribution of lipid stack height, width, and density with four SP-B truncation peptides: SP-B 1-25, SP-B 9 -25, SP-B 11-25, and SP-B 1-25Nflex (prolines 2 and 4 substituted with alanine). The first nine amino acids, termed the insertion sequence and the interface seeking tryptophan residue 9, are shown to stabilize the formation of nanosilos while an increase in the insertion sequence flexibility (SP-B 1-25Nflex) may improve peptide functionality. This provides a functional understanding of the insertion sequence beyond anchoring the protein to the two-dimensional membrane lining the lung, as it also stabilizes formation of nanosilos, creating reversible repositories for fluid lipids at high compression. In lavaged, surfactant-deficient rats, instillation of a mixture of SP-B 1-25 (as a monomer or dimer) and synthetic lung lavage lipids quickly improved oxygenation and dynamic compliance, whereas SP-B 11-25 surfactants showed oxygenation and dynamic compliance values similar to that of lipids alone, demonstrating a positive correlation between formation of stable, but reversible, nanosilos and in vivo efficacy.
Orientation and depth of surfactant protein B C-terminal helix in lung surfactant bilayers
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2012
a b s t r a c t SP-B CTERM is a cationic amphipathic helical peptide and functional fragment composed of residues 63 to 78 of surfactant protein B (SP-B). Static oriented and magic angle spinning solid state NMR, along with molecular dynamics simulation was used to investigate its structure, orientation, and depth in lipid bilayers of several compositions, namely POPC, DPPC, DPPC/POPC/POPG, and bovine lung surfactant extract (BLES). In all lipid environments the peptide was oriented parallel to the membrane surface. While maintaining this approximately planar orientation, SP-B CTERM exhibited a flexible topology controlled by subtle variations in lipid composition. SP-B CTERM -induced lipid realignment and/or conformational changes at the level of the head group were observed using 31 P solid-state NMR spectroscopy. Measurements of the depth of SP-B CTERM indicated the peptide center positions~8 Å more deeply than the phosphate headgroups, a topology that may allow the peptide to promote functional lipid structures without causing micellization upon compression. j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / b b a m e m 1166 P. Bertani et al.
Proceedings of the National Academy of Sciences, 1990
We have synthesized pulmonary surfactant apoprotein SP-B peptides by solid-phase chemistry and demonstrated their ability to enhance the surface-active properties of synthetic lipid mixtures. The synthetic peptides were reactive with antiserum generated against the native bovine surfactant peptide. Both peptides conferred surfactant-like properties to synthetic lipid mixtures as assessed by a Wilhelmy balance and pulsating bubble surfactometer. Likewise, mixtures of synthetic SP-B peptides and lipid restored compliance of isolated surfactant-deficient rat lungs. This work demonstrates the utility of SP-B as a functional component of pulmonary surfactant mixtures for treatment of respiratory distress syndrome or other disorders characterized by surfactant deficiency.
The pulmonary surfactant protein C (SP-C) precursor is a type II transmembrane protein
Biochemical Journal, 1991
Human pulmonary-surfactant-associated protein C (SP-C) is an extremely hydrophobic peptide comprising 34-35 amino acids. It is involved in the reduction of surface tension at the air/liquid in the lung. In order to understand the mechanism by which this molecule is generated from its 197-amino-acid-residues-long precursor and secreted into the alveolar space, we analysed the biosynthesis and processing of this precursor in an ‘in vitro’ system. Our results show that the SP-C precursor is a 21 kDa integral membrane protein. It is anchored in the membrane by a hydrophobic domain that comprises the 20-amino-acid-residues-long hydrophobic core of the mature SP-C peptide. The N-terminus remains in the cytoplasm, which leads to a type II transmembrane orientation of the precursor. Membrane integration occurs in a signal-peptidase-independent manner. The hydrophobic domain acts as both signal sequence and membrane-anchoring domain. We suggest that correct membrane insertion of the SP-C pre...
1 BIOPHYSICAL CHARACTERIZATION OF PEPTIDE MIMICS OF LUNG SURFACTANT PROTEIN-B By
2008
I thank my mentor Dr. Joanna Long for providing me the opportunity for working in her laboratory. I thank her for her support, patience, sense of humor, and kindness. I hope to acquire some of those qualities that she has as I continue to mature and develop. I would also like to offer my gratitude to members of my committee: Dr. Arthur Edison, Dr. Robert McKenna, Dr. Susan Frost and Dr. Ron Castellano. I appreciate their support and their help. I am particularly grateful for Dr. Susan Frost for giving me some extra support with regards to my presentation and for her willingness to afford some of her time to look over my dissertation. I want to extend my heartfelt gratitude and sincere thanks to members of the laboratory
A model for the structure and mechanism of action of pulmonary surfactant protein B
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2015
Surfactant protein B (SP-B), from the saposin-like family of proteins, is essential to facilitate the formation and proper performance of surface active films at the air-liquid interface of mammalian lungs, and lack of or deficiency in this protein is associated with lethal respiratory failure. Despite its importance, neither a structural model nor a molecular mechanism of SP-B is available. The purpose of the present work was to purify and characterize native SP-B supramolecular assemblies to provide a model supporting structure-function features described for SP-B. Purification of porcine SP-B using detergent-solubilized surfactant reveals the presence of 10 nm ring-shaped particles. These rings, observed by atomic force and electron microscopy, would be assembled by oligomerization of SP-B as a multimer of dimers forming a hydrophobically coated ring at the surface of phospholipid membranes or monolayers. Docking of rings from neighboring membranes would lead to formation of SP-B...
Biochemistry, 2005
Pulmonary surfactant protein SP-B is absolutely required for proper function of surfactant in the alveoli, and is an important component of therapeutical surfactant preparations used to treat respiratory pathologies. To explore inherent structural and functional determinants within the amino acid sequence of mature SP-B, porcine SP-B has been subjected to extensive disulfide reduction under highly denaturing conditions and to cysteine carboxyamidomethylation, and the structure, lipid-protein interactions, and surface activity of this modified form have been characterized. Refolding of the reduced protein yielded a form (SP-Br) with secondary structure practically identical to that of the native disulfide-linked SP-B dimer. Reduced SP-Br exhibited higher structural flexibility than native SP-B, as indicated by a higher susceptibility of fluorescence emission to quenching by acrylamide and biphasic behavior during interaction of the protein with lipid bilayers and monolayers. SP-Br had, however, effects similar to those of native SP-B on the thermotropic properties of dipalmitoylphosphatidylcholine (DPPC) bilayers. SP-Br was more effective than native SP-B in promoting interfacial adsorption of phospholipid bilayers into interfacial films, presumably because of its higher structural flexibility, and retained the ability of native SP-B to stabilize DPPC interfacial films compressed to pressures near collapse against spontaneous relaxation. SP-Br also mimicked the behavior of native SP-B in lipid-protein films subjected to dynamic compressionexpansion cycling in a captive bubble surfactometer, but only in the presence of phosphatidylglycerol (PG), the main anionic phospholipid in surfactant. The presence of PG appears to be required for SP-Br to acquire the appropriate tertiary folding to produce progressively more efficient lipid-protein films capable of reaching very high pressures upon limited compression with almost no hysteresis.