Showing papers by "Richard M. Epand published in 1984"
TL;DR: The ability of the peptides to fold into amphiphatic structures can enhance their lipid binding affinity, as indicated by the higher affinity for DMPC of N-t-Boc-beta-Ala-Trp-Met-Asp-Phe-NH2 as compared to its "reversed" analogue.
Abstract: The binding of pentagastrin and three other structurally related pentapeptides to phospholipid vesicles has been studied by fluorescence spectroscopy. The fluorescence of the tryptophan residues of these peptides exhibits an increased quantum yield upon binding to phospholipid vesicles. This is accompanied by a blue shift of the maximum emission, indicative of the incorporation of the tryptophan residue into a more hydrophobic environment. The affinity of the peptides for a zwitterionic phospholipid, dimyristoylphosphatidylcholine (DMPC), increases in the following order: N-t-Boc-beta-Ala-Trp-Met-Gly-Phe-NH2 greater than N-t-Boc-beta-Ala-Trp-Met-Arg-Phe-NH2 greater than N-t-Boc-beta-Ala-Trp-Met-Asp-Phe-NH2 greater than N-t-Boc-beta-Ala-Trp-Met-Phe-Asp-NH2. Comparison of the interaction of these various peptides with this phospholipid indicates that although the interaction is largely of hydrophobic nature, the structure of the polar amino acids and their electrostatic charge have significant influence on the nature of the bindings. In addition, the sequence of polar and apolar amino acids appears to be of importance. The higher affinity for DMPC of N-t-Boc-beta-Ala-Trp-Met-Asp-Phe-NH2 as compared to its "reversed" analogue N-t-Boc-beta-Ala-Trp-Met-Phe-Asp-NH2 suggests that the ability of the peptides to fold into amphiphatic structures can enhance their lipid binding affinity. For all peptides the interaction with DMPC is greater at 8 degrees C, i.e., below the lipid phase transition temperature, than at 40 degrees C, i.e., above the lipid phase transition temperature.(ABSTRACT TRUNCATED AT 250 WORDS)
98 citations
TL;DR: A novel aspect of the role of glucagon as a calcium-mobilizing agent is demonstrated by the decrease in the maximal velocities induced by glucagon of both calcium transport and (Ca2+-Mg2+)-ATPase activity.
63 citations
01 Nov 1984
TL;DR: The molecular basis for preferential interaction with gel state lipid is suggested to be the ability of proteins to self-associate, probably at defect sites, below the phase transition temperature and thereby increase protein-protein interactions while maintaining protein-lipid and lipid-lipids interactions.
Abstract: This review is not a comprehensive study of the broad area of lipid-protein interactions, but rather concentrates on the question of the effect of phase transitions on the interaction of peptides and proteins with phospholipids. Before considering the relative ability of peptides and proteins to incorporate into phospholipid bilayers in the gel or the liquid crystalline state, we briefly review the variety of effects of proteins on lipid phase transitions. It is essential to be cognizant of these effects when discussing how phase transitions affect protein incorporation. The effect of proteins on lipid order and motion above and below the phase transition is discussed and the current state of knowledge on this topic is briefly reviewed. In discussing the thermodynamics of lipid-protein association and the effect of phase transitions one must deal with systems at equilibrium, a state often difficult to achieve with high molecular weight aggregates. It is demonstrated that there are a variety of effects of phase transitions on protein incorporation. Some proteins incorporate more readily into liquid crystalline state lipid; others incorporate only in a narrow temperature region around the phase transition temperature, while still others interact with lipid over a broad range of temperatures while exhibiting some preference for interacting with gel state lipid. The molecular basis for preferential interaction with gel state lipid is suggested to be the ability of proteins to self-associate, probably at defect sites, below the phase transition temperature and thereby increase protein-protein interactions while maintaining protein-lipid and lipid-lipid interactions.+
25 citations
TL;DR: The effects of the myelin basic protein on either carboxyfluorescein release or vesicle aggregation were similar to, although somewhat greater than, that of poly‐l‐lysine; the aggregation of vesicles containing degradation products of phosphatidylethanolamine can be ascribed largely to the presence of aliphatic aldehydes.
Abstract: The capacity of myelin basic protein or of poly-l-lysine to promote leakage of carboxyfluorescein from vesicles or the aggregation of vesicles was studied. The vesicles were composed of phosphatidylcholine as the sole or major lipid component. Addition of 10% sphingomyelin, 10% phosphatidylglycerol, 10% egg or bovine brain phosphatidylethanolamine, or 30% dodecanal had relatively little effect on the extent of carboxyfluorescein release in the presence of either myelin basic protein or poly-l-lysine. In contrast with these results, the extent of vesicle aggregation was very sensitive to lipid composition. Addition of 10% phosphatidylglycerol induced more aggregation than the other phospholipids tested. Admixing 10% of a partially degraded sample of bovine brain phosphatidylethanolamine also led to a large amount of aggregation induced by the myelin basic protein. This latter aggregation appeared more specific for the basic protein, as it occurred to a much smaller extent with poly-l-lysine. In general, the effects of the myelin basic protein on either carboxyfluorescein release or vesicle aggregation were similar to, although somewhat greater than, that of poly-l-lysine. The aggregation of vesicles containing degradation products of phosphatidylethanolamine can be ascribed largely to the presence of aliphatic aldehydes. The effect of aliphatic aldehydes was specific in that the aliphatic alcohol, hexadecanol, or the short-chain aldehydes, acetaldehyde or butyraldehyde, did not promote myelin basic protein-induced vesicle aggregation. In addition, poly-l-lysine was less effective than the basic protein in aggregating vesicles containing aliphatic aldehydes. Other proteins such as bovine serum albumin and ribonuclease had no effect. Aliphatic aldehydes are produced as a result of the degradation of plasmalogens, a class of phospholipids abundant in myelin. Plasmalogenase activity is elevated in multiple sclerosis. The interaction between myelin basic protein and membranes containing aldehydes may thus be of particular biological importance.
16 citations
TL;DR: The lipid mixtures involving the first two solutes listed above exhibited approximately symmetrical curves of excess apparent specific heat vs. temperature, while the curves for the other solutes were asymmetric, and could be well represented as the sum of either two or three two-state curves.
9 citations
TL;DR: Human myelin basic protein isolated from the brains of individuals who died with multiple sclerosis was more potent in inducing the aggregation of egg phosphatidylcholine vesicles than was the basic protein isolate from the minds of normal individuals.
Abstract: Human myelin basic protein isolated from the brains of individuals who died with multiple sclerosis was more potent in inducing the aggregation of egg phosphatidylcholine vesicles than was the basic protein isolated from the brains of normal individuals. The portion of myelin basic protein which bound to egg phosphatidylcholine vesicles was separated from the free protein by sucrose density gradient centrifugation. Similar amounts of basic protein from normal or from multiple sclerosis brains are bound to the lipid and no consistent differences in the NG, N′G dimethyl-arginine content of the protein fractions have been found.
8 citations
TL;DR: There was a much greater increase in carboxyfluorescein leakage from phosphatidylglycerol-containing vesicles induced by salmon calcitonin demonstrating the greater ability of the peptide to rupture bilayers containing this phospholipid.
8 citations