The orientation and dynamics of substance P in lipid environments

Abstract

The membrane-associated conformation of substance P (RPKPQQFFGLM-NH2) has been previously proposed to be the NKI-receptor-active conformation. In this work, NMR methods are applied to explore the orientation and dynamics of substance P at lipid surfaces for which the peptide's three-dimensional structure had been previously determined. Here the presence of dodecylphosphocholine (DPC) or sodium dodecylsulfate (SDS) micelles has been found to cause sequence specific changes in the acid-and base-catalyzed amide proton exchange rates relative to the solution state values. On binding of substance P to SDS micelles, the FFG portion showed the largest decreases in the base-catalyzed amide exchange rates. Similar sequence-specific changes in substance P are observed in the presence of DPC micelles, albeit at much weaker levels due to fast exchange between free and bound forms of the peptide. These differences are attributed to the location of the amide protons either in the surface double layer (via electrostatic effect) or inserted into the polar head group region of the micelles (via low dielectric). The sequence-specific effects of micelle association were also observed in the homonuclear nonselective spin-lattice relaxation time; these, in combination with spin-spin relaxation times, were used to calculate correlation times for the backbone amide protons. These data combined with paramagnetic broadening observations on peptide protons in the presence of spin-labeled lipids yield a detailed model of the interaction of substance P with lipid surfaces.Keywords: amide exchange; correlation times; dodecylphosphocholine; NMR; peptide-lipid interactions; sodium dodecylsulfate; substance P; TI and T2 relaxation Substance P (SP) is a member of the tachykinin family of neuropeptides and is widely distributed in both the central and peripheral nervous system of humans. Tachykinins, which are characterized by a common C-terminal tail (F-x-GLM-NH2 where x is F or V for mammals), are of biomedical interest because they have been shown to cause hypotension, contraction of smooth muscles, salivation, transmission of pain, and inflammation (Pernow, 1983). Ligands of SP receptors have potential as a novel class of anti-inflammatory or pain medication, and as a result, interest is high in the structural elements of the peptide that may control receptor activity and selectivity.The membrane-bound conformation of SP has been proposed to be the NK1 receptor active form (Schwyzer, 1995), and the three-dimensional structure of SP in the presence of Abbreviations: DPC, dodecylphosphocholine; RMSD, root-mean-square deviation; SDS, sodium dodecylsulfate; SP, substance P; 2D TOCSY, twodimensional total correlation spectroscopy. 1996). Both structures were similar, although fast exchange between free and bound forms was observed for SP with DPC micelles and predominantly bound characteristics were found for SP with SDS micelles.The three-dimensional SP structure at these lipid-membrane mimetics may represent either a receptor-bound co...

Recognition of GPCRs by Peptide Ligands and Membrane Compartments theory: Structural Studies of Endogenous Peptide Hormones in Membrane Environment

“…The conserved C-terminal hydrophobic residues (Table 1) are localized on the same side of the peptide as has been observed in the DPC-bound peptide [56]. Neutron diffraction and amide-exchange experiments have been carried out to investigate the interactions of SP and NKA with the micelles or phospholipids bilayers [179][180][181]. Amide-exchange experiments in SDS micelles suggest interactions of Phe8, Phe9 and Gly10 residues in the interfacial region of the lipid micelle headgroups [179].…”

“…Neutron diffraction and amide-exchange experiments have been carried out to investigate the interactions of SP and NKA with the micelles or phospholipids bilayers [179][180][181]. Amide-exchange experiments in SDS micelles suggest interactions of Phe8, Phe9 and Gly10 residues in the interfacial region of the lipid micelle headgroups [179]. Neutron diffraction experiments clearly demonstrate that SP interacts with both zwitterionic and anionic membranes and the C-terminus of the peptide is positioned at a depth below the membrane surface [180].…”

The study of the conformation and interaction of two tachykinin peptides in membrane mimicking systems by NMR spectroscopy and pulsed field gradient diffusion

“…3,4 The interaction of SP with lipid monolayers and bilayers has been investigated extensively in the past. [5][6][7][8][9][10][11][12][13][14] Seelig and Macdonald concluded that SP does not insert into zwitterionic palmitoyloleoylphosphatidylcholine monolayers, 5 but does insert into monolayers with negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-glycerol monolayers. It was proposed by Schwyzer that SP interacts with its receptors through a membranemediated mechanism, 6,7 but this mechanism was disputed by Seelig et al for several SP agonists.…”

APAP, a sequence‐pattern recognition approach identifies substance P as a potential apoptotic peptide

“…SP is known to form an K-helical structure in hydrophobic environments but not in aqueous solution [23], while it has a positive charge distribution over its sequence, supporting the ¢nding that SP is a PAP. Therefore, the neuropeptide SP was tested for its preference for mitochondria-like membranes.…”