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Biochemistry Jan 2008Phospholamban (PLN) and sarcolipin (SLN) are two single-pass membrane proteins that regulate Ca2+-ATPase (SERCA), an ATP-driven pump that translocates calcium ions into... (Review)
Review
Phospholamban (PLN) and sarcolipin (SLN) are two single-pass membrane proteins that regulate Ca2+-ATPase (SERCA), an ATP-driven pump that translocates calcium ions into the lumen of the sarcoplasmic reticulum, initiating muscle relaxation. Both proteins bind SERCA through intramembrane interactions, impeding calcium translocation. While phosphorylation of PLN at Ser-16 and/or Thr-17 reestablishes calcium flux, the regulatory mechanism of SLN remains elusive. SERCA has been crystallized in several different states along the enzymatic reaction coordinates, providing remarkable mechanistic information; however, the lack of high-resolution crystals in the presence of PLN and SLN limits the current understanding of the regulatory mechanism. This brief review offers a survey of our hybrid structural approach using solution and solid-state NMR methodologies to understand SERCA regulation from the point of view of PLN and SLN. These results have improved our understanding of the calcium translocation process and are the basis for designing new therapeutic approaches to ameliorate muscle malfunctions.
Topics: Calcium; Calcium-Binding Proteins; Calcium-Transporting ATPases; Magnetic Resonance Spectroscopy; Models, Molecular; Muscle Proteins; Protein Binding; Protein Conformation; Protein Structure, Secondary; Proteolipids
PubMed: 18081313
DOI: 10.1021/bi701668v -
Biochimica Et Biophysica Acta Nov 1998Pulmonary surfactant contains less than 1 wt% of the very non-polar surfactant protein C (SP-C). In most animal species the major form of SP-C is a 35-residue peptide... (Review)
Review
Pulmonary surfactant contains less than 1 wt% of the very non-polar surfactant protein C (SP-C). In most animal species the major form of SP-C is a 35-residue peptide chain which contains two thioester-linked palmitoyl groups, giving a total molecular mass of 4.2 kDa. Several minor variants of SP-C exist, formed from N-terminal truncation, lysine palmitoylation, methionine oxidation and C-terminal esterification. The primary structure is evolutionarily conserved and SP-C appears to be the only constituent which is unique to pulmonary surfactant, indicating important and specific functions. The three-dimensional structure in an aqueous mixed organic solvent determined by NMR spectroscopy revealed one continuous 37 A long alpha-helix encompassing residues 9-34 as the only regular structural element. The central 23 A of the helix contains exclusively aliphatic residues with branched side-chains, mainly valines, and exposes an all-hydrophobic regular surface. The size of the entire helix perfectly matches the thickness of a fluid dipalmitoylphosphatidylcholine membrane, and the all-hydrophobic part of the helix matches the acyl-chain part of such a bilayer. This supports a transmembrane orientation of SP-C in pulmonary surfactant bilayers. In a phospholipid monolayer, the SP-C helix is tilted, thereby maximizing the interactions with the lipid acyl-chains also in this environment. The palmitoylcysteines of SP-C, which are located in the flexibly disordered N-terminal octapeptide segment, appear to be important both for integrity of the alpha-helical structure and for functional properties. Since the conformation of the N-terminal part in a phospholipid environment is not known, the mechanisms whereby the SP-C thioester-linked palmitoyl chains affect structure and function remain to be determined.
Topics: Amino Acid Sequence; Molecular Sequence Data; Phospholipids; Protein Conformation; Protein Isoforms; Proteolipids; Pulmonary Surfactants; Structure-Activity Relationship
PubMed: 9813304
DOI: 10.1016/s0925-4439(98)00065-9 -
Current Biology : CB Jan 2001Recent results suggest that membrane proteins are delivered to the myelin sheath of an oligodendrocyte on rafts with a distinctive lipid composition. The major intrinsic... (Review)
Review
Recent results suggest that membrane proteins are delivered to the myelin sheath of an oligodendrocyte on rafts with a distinctive lipid composition. The major intrinsic membrane protein of myelin, proteolipid protein, interacts with rafts in oligodendrocytes but not with the different rafts found in other cell types.
Topics: Lipids; Myelin Proteolipid Protein
PubMed: 11231143
DOI: 10.1016/s0960-9822(01)00008-2 -
Scientific Reports Feb 2022Malignant melanoma is the main cause of death in patients with skin cancer. Overexpression of Proteolipid protein 2 (PLP2) increased tumor metastasis and the knockdown...
Malignant melanoma is the main cause of death in patients with skin cancer. Overexpression of Proteolipid protein 2 (PLP2) increased tumor metastasis and the knockdown of PLP2 inhibited the growth and metastasis of melanoma cells. In the present work, we studied the antitumor activity of peptide Rb4 derived from protein PLP2. In vitro, Rb4 induced F-actin polymerization, prevented F-actin depolymerization and increased the ER-derived cytosolic calcium. Such effects were associated with necrosis of murine melanoma B16F10-Nex2 cells and with inhibition of the viability of human cancer cell lines. Loss of plasma membrane integrity, dilation of mitochondria, cytoplasm vacuolation and absence of chromatin condensation characterized tumor cell necrosis. Cleavage of PARP-1 and inhibition of RIP1 expression were also observed. In vivo, peptide Rb4 reduced the lung metastasis of tumor cells and delayed the subcutaneous melanoma growth in a syngeneic model. Rb4 induced the expression of two DAMPs molecules, HMGB1 and calreticulin, in B16F10-Nex2. Our results suggest that peptide Rb4 acts directly on tumor cells inducing the expression of DAMPs, which trigger the immunoprotective effect in vivo against melanoma cells. We suggest that peptide Rb4 is a promising compound to be developed as an anticancer drug.
Topics: Animals; Antineoplastic Agents; Calreticulin; Cell Death; Cell Line, Tumor; Gene Expression; HMGB1 Protein; Humans; MARVEL Domain-Containing Proteins; Melanoma; Mice; Necrosis; Nuclear Pore Complex Proteins; Peptides; Poly (ADP-Ribose) Polymerase-1; Proteolipids; RNA-Binding Proteins; Skin Neoplasms
PubMed: 35190586
DOI: 10.1038/s41598-022-06429-8 -
Biochemical and Biophysical Research... Mar 2022L-enantiomers of antimicrobial peptides (AMPs) are sensitive to proteolytic degradation; however, D-enantiomers of AMPs are expected to provide improved proteolytic... (Comparative Study)
Comparative Study
L-enantiomers of antimicrobial peptides (AMPs) are sensitive to proteolytic degradation; however, D-enantiomers of AMPs are expected to provide improved proteolytic resistance. The present study aimed to comparatively investigate the in vitro antibacterial activity, trypsin and serum stability, toxicity, and in vivo antibacterial activity of L-enantiomeric bovine NK2A (L-NK2A) and its D-enantiomeric NK2A (D-NK2A). Circular dichroism spectroscopy of D-NK2A and L-NK2A in anionic liposomes showed α-helical structures and the α-helical conformation of D-NK2A was a mirror image of L-NK2A. Both D-NK2A and L-NK2A displayed minimal in vitro and in vivo toxicities. RP-HPLC and mass spectrometry analyses revealed that D-NK2A, but not L-NK2A, was resistant to trypsin digestion. D-NK2A and L-NK2A showed similar in vitro bacterial killing activities against Histophilus somni. Slightly reduced antibacterial activity was observed when D-NK2A and L-NK2A were pre-incubated with serum. Confocal and transmission electron microscopic findings confirmed that both peptides induced disruption of bacterial inner- and outer-membranes. Improved survivals with D-NK2A treatment were observed when compared to L-NK2A in a murine model of acute H. somni septicemia. We conclude that antibacterial activity and mode of action of NK2A are not chiral specific. With further optimization, D-NK2A may be a viable AMP candidate to combat bacterial infections.
Topics: Animals; Anti-Bacterial Agents; Antimicrobial Peptides; Cattle; Circular Dichroism; Kaplan-Meier Estimate; Mice; Microscopy, Electron, Transmission; Pasteurellaceae; Pasteurellaceae Infections; Protein Stability; Protein Structure, Secondary; Proteolipids; Stereoisomerism
PubMed: 35101666
DOI: 10.1016/j.bbrc.2022.01.071 -
Biochimica Et Biophysica Acta Nov 2000The physico-chemical properties of short-chain phosphatidylcholine are reviewed to the extent that its biological activity as a mild detergent can be rationalized.... (Comparative Study)
Comparative Study Review
The physico-chemical properties of short-chain phosphatidylcholine are reviewed to the extent that its biological activity as a mild detergent can be rationalized. Long-chain diacylphosphatidylcholines are typical membrane phospholipids that form preferentially smectic lamellar phases (bilayers) when dispersed in water. In contrast, the preferred phase of the short-chain analogues dispersed in excess water is the micellar phase. The preferred conformation and the dynamics of short-chain phosphatidylcholines in the monomeric and micellar state present in H(2)O are discussed. The motionally averaged conformation of short-chain phosphatidylcholines is then compared to the single-crystal structures of membrane lipids. The main conclusion emerging is that in terms of preferred conformation and motional averaging short-chain phosphatidylcholines closely resemble their long-chain analogues. The dispersing power of short-chain phospholipids is emphasized in the second part of the review. Evidence is presented to show that this class of compounds is superior to most other detergents used in the solubilization of membrane proteins and the reconstitution of the solubilized proteins to artificial membrane systems (proteoliposomes). The prominent feature of the solubilization/reconstitution of integral membrane proteins by short-chain PC is the retention of the native protein structure and hence the protein function. Due to their special detergent-like properties, short-chain PC lend themselves very well not only to membrane solubilization but also to the purification of integral membrane proteins. The retention of the native protein structure in the solubilized state, i.e. in mixed micelles consisting of the integral membrane protein, intrinsic membrane lipids and short-chain PC, is rationalized. It is hypothesized that short-chain PC interacts primarily with the lipid bilayer of a membrane and very little if at all with the membrane proteins. In this way, the membrane protein remains associated with its preferred intrinsic membrane lipids and retains its native structure and its function.
Topics: Detergents; Magnetic Resonance Spectroscopy; Membrane Proteins; Micelles; Molecular Conformation; Phosphatidylcholines; Phospholipids; Protein Conformation; Proteolipids; Solubility; Terminology as Topic
PubMed: 11090824
DOI: 10.1016/s0304-4157(00)00008-3 -
Molecular Neurobiology Aug 2009Fast-transmitting vertebrate axons are electrically insulated with multiple layers of nonconductive plasma membrane of glial cell origin, termed myelin. The myelin... (Review)
Review
Fast-transmitting vertebrate axons are electrically insulated with multiple layers of nonconductive plasma membrane of glial cell origin, termed myelin. The myelin membrane is dominated by lipids, and its protein composition has historically been viewed to be of very low complexity. In this review, we discuss an updated reference compendium of 342 proteins associated with central nervous system myelin that represents a valuable resource for analyzing myelin biogenesis and white matter homeostasis. Cataloging the myelin proteome has been made possible by technical advances in the separation and mass spectrometric detection of proteins, also referred to as proteomics. This led to the identification of a large number of novel myelin-associated proteins, many of which represent low abundant components involved in catalytic activities, the cytoskeleton, vesicular trafficking, or cell adhesion. By mass spectrometry-based quantification, proteolipid protein and myelin basic protein constitute 17% and 8% of total myelin protein, respectively, suggesting that their abundance was previously overestimated. As the biochemical profile of myelin-associated proteins is highly reproducible, differential proteome analyses can be applied to material isolated from patients or animal models of myelin-related diseases such as multiple sclerosis and leukodystrophies.
Topics: Animals; Demyelinating Diseases; Humans; Myelin Proteins; Myelin Sheath; Proteolipids; Proteomics
PubMed: 19452287
DOI: 10.1007/s12035-009-8071-2 -
BMC Biology Feb 2024Membranes are protein and lipid structures that surround cells and other biological compartments. We present a conceptual model wherein all membranes are organized into...
Membranes are protein and lipid structures that surround cells and other biological compartments. We present a conceptual model wherein all membranes are organized into structural and functional zones. The assembly of zones such as receptor clusters, protein-coated pits, lamellipodia, cell junctions, and membrane fusion sites is explained to occur through a protein-lipid code. This challenges the theory that lipids sort proteins after forming stable membrane subregions independently of proteins.
Topics: Proteolipids; Membranes; Carrier Proteins; Cell Membrane
PubMed: 38414038
DOI: 10.1186/s12915-024-01849-6 -
Cells Apr 2021The gene encodes a 17-kDa protein containing four putative transmembrane segments whose expression is restricted to human T cells, polarized epithelial cells and... (Review)
Review
The gene encodes a 17-kDa protein containing four putative transmembrane segments whose expression is restricted to human T cells, polarized epithelial cells and myelin-forming cells. The MAL protein has two unusual biochemical features. First, it has lipid-like properties that qualify it as a member of the group of proteolipid proteins. Second, it partitions selectively into detergent-insoluble membranes, which are known to be enriched in condensed cell membranes, consistent with MAL being distributed in highly ordered membranes in the cell. Since its original description more than thirty years ago, a large body of evidence has accumulated supporting a role of MAL in specialized membranes in all the cell types in which it is expressed. Here, we review the structure, expression and biochemical characteristics of MAL, and discuss the association of MAL with raft membranes and the function of MAL in polarized epithelial cells, T lymphocytes, and myelin-forming cells. The evidence that MAL is a putative receptor of the epsilon toxin of , the expression of MAL in lymphomas, the hypermethylation of the gene and subsequent loss of MAL expression in carcinomas are also presented. We propose a model of MAL as the organizer of specialized condensed membranes to make them functional, discuss the role of MAL as a tumor suppressor in carcinomas, consider its potential use as a cancer biomarker, and summarize the directions for future research.
Topics: Animals; Cell Membrane; Epithelial Cells; Humans; Lymphocytes; Myelin and Lymphocyte-Associated Proteolipid Proteins; Neoplasms; Schwann Cells
PubMed: 33946345
DOI: 10.3390/cells10051065 -
Biophysical Journal Jan 2020Membrane proteins are embedded in a complex lipid environment that influences their structure and function. One key feature of nearly all biological membranes is a...
Membrane proteins are embedded in a complex lipid environment that influences their structure and function. One key feature of nearly all biological membranes is a distinct lipid asymmetry. However, the influence of membrane asymmetry on proteins is poorly understood, and novel asymmetric proteoliposome systems are beneficial. To our knowledge, we present the first study on a multispanning protein incorporated in large unilamellar liposomes showing a stable lipid asymmetry. These asymmetric proteoliposomes contain the Na/H antiporter NhaA from Salmonella Typhimurium. Asymmetry was introduced by partial, outside-only exchange of anionic phosphatidylglycerol (PG), mimicking this key asymmetry of bacterial membranes. Outer-leaflet and total fractions of PG were determined via ζ-potential (ζ) measurements after lipid exchange and after scrambling of asymmetry. ζ-Values were in good agreement with exclusive outside localization of PG. The electrogenic Na/H antiporter was active in asymmetric liposomes, and it can be concluded that reconstitution and generation of asymmetry were successful. Lipid asymmetry was stable for more than 7 days at 23°C and thus enabled characterization of the Na/H antiporter in an asymmetric lipid environment. We present and validate a simple five-step protocol that addresses key steps to be taken and pitfalls to be avoided for the preparation of asymmetric proteoliposomes: 1) optimization of desired lipid composition, 2) detergent-mediated protein reconstitution with subsequent detergent removal, 3) generation of lipid asymmetry by partial exchange of outer-leaflet lipid, 4) verification of lipid asymmetry and stability, and 5) determination of protein activity in the asymmetric lipid environment. This work offers guidance in designing asymmetric proteoliposomes that will enable researchers to compare functional and structural properties of membrane proteins in symmetric and asymmetric lipid environments.
Topics: Lipids; Proteolipids; Salmonella typhimurium; Unilamellar Liposomes
PubMed: 31843262
DOI: 10.1016/j.bpj.2019.10.043