scholarly journals Synthetic putative transmembrane region of minimal potassium channel protein (minK) adopts an α-helical conformation in phospholipid membranes

1997 ◽  
Vol 325 (2) ◽  
pp. 475-479 ◽  
Author(s):  
Eric A. J. MERCER ◽  
Geoffrey W. ABBOTT ◽  
Stephen P. BRAZIER ◽  
Bala RAMESH ◽  
Parvez I. HARIS ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Potassium Channel ◽  
Transmembrane Domain ◽  
Cd Spectroscopy ◽  
Helical Conformation ◽  
Phospholipid Membranes ◽  
Transmembrane Region ◽  
Aqueous Buffer ◽  
Channel Protein ◽  
Β Sheet

Minimal potassium channel protein (minK) is a potassium channel protein consisting of 130 amino acids, possessing just one putative transmembrane domain. In this study we have synthesized a peptide with the amino acid sequence RDDSKLEALYILMVLGFFGFFTLGIMLSYI, containing the putative transmembrane region of minK, and analysed its secondary structure by using Fourier-transform IR and CD spectroscopy. The peptide was virtually insoluble in aqueous buffer, forming intermolecular β-sheet aggregates. On attempted incorporation of the peptide into phospholipid membranes with a method involving dialysis, the peptide adopted a predominantly intermolecular β-sheet conformation identical with that of the peptide in aqueous buffer, in agreement with a previous report [Horvàth, Heimburg, Kovachev, Findlay, Hideg and Marsh, (1995) Biochemistry 34, 3893–3898]. However, by using an alternative method of incorporating the peptide into phospholipid membranes we found that the peptide adopted a predominantly α-helical conformation, a finding consistent with various proposed structural models. These observed differences in secondary structure are due to artifacts of aggregation of the peptide before incorporation into lipid.

Secondary Structure of Decorin-Derived Peptides in Solution

MRS Advances ◽  
2016 ◽  
Vol 1 (27) ◽  
pp. 1965-1970
Author(s):  
Axel T. Neffe ◽  
Stefania Federico ◽  
Andreas Lendlein
Keyword(s):  
Crystal Structure ◽  
Outer Surface ◽  
Cd Spectroscopy ◽  
Helical Conformation ◽  
Structural Elements ◽  
Original Sequence ◽  
X Ray ◽  
Inner Surface ◽  
Β Sheet ◽  
Secondary Structural Elements

ABSTRACTDecorin is a small leucine-rich repeat proteoglycan supporting collagen fibril formation by controlling the rate of collagen fibrillogenesis and fibril dimensions. Peptides derived from the inner surface of decorin have been shown to bind to collagen, while peptides derived from the outer surface do not display such binding affinity. As typical secondary structural elements such as β-sheets and α-helical regions were found in the decorin X-ray crystal structure, here it was investigated by Circular Dichroism (CD) spectroscopy in solution, whether the same structural elements can be found in the derived peptides. Here it is shown that the peptide derived from decorin’s outer surface has the propensity to adopt helical conformation, as it was found in the crystal structure. The results were more pronounced in 80 vol% TFE solution, which led to an increase in the number as well as the length of helices. In contrast, peptides derived from the inner surface had a higher tendency to adopt β-sheet conformation, also in TFE, which corresponds to the conformation of the original sequence in the crystal structure of decorin. This suggests that the peptides derived from decorin adopt the structures present in the native protein.

scholarly journals Effect of temperature on the secondary structure of β-lactoglobulin at pH 6.7, as determined by CD and IR spectroscopy: a test of the molten globule hypothesis

1997 ◽  
Vol 324 (1) ◽  
pp. 341-346 ◽  
Author(s):  
Xiao Lin QI ◽  
Carl HOLT ◽  
David MCNULTY ◽  
David T. CLARKE ◽  
Sharon BROWNLOW ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Molten Globule ◽  
Cd Spectroscopy ◽  
Helical Conformation ◽  
Effect Of Temperature ◽  
Sheet Structure ◽  
Good Signal ◽  
Increasing Temperature ◽  
Β Lactoglobulin ◽  
Β Sheet

Previous CD measurements of changes in the conformation of β-lactoglobulin at neutral pH as a function of temperature indicated the formation of a molten globule state above approx. 70 °C. New CD measurements are reported at temperatures up to 80 °C with an instrument on the Daresbury synchrotron radiation source which gives spectra of good signal-to-noise ratio down to 170 nm. IR spectra were recorded up to 94.8 °C with a ZnSe circle cell and a single simplified model of the substructure of the amide I′ band was used to give the fractional contents of β-sheet structure unambiguously and independently of the CD spectroscopy. The results of both techniques, however, were in agreement in showing a progressive loss of β-sheet structure with increasing temperature, beginning below the denaturation temperature. Nevertheless, the CD spectroscopy showed a fairly abrupt loss of virtually all the helical conformation at approx. 65 °C. Comparison of the present results with other studies on the molten globule formed at acid pH in the lipocalin family suggests that above 65 °C a partly unfolded state is formed, possibly by destabilization of the intermolecular β-strand I and the loss of the main helix, but it is not a classical molten globule transition.

Scorpion toxin-potassium channel interaction law and its applications.

2020 ◽  
Vol 01 ◽  
Author(s):  
Zheng Zuo ◽  
Zongyun Chen ◽  
Zhijian Cao ◽  
Wenxin Li ◽  
Yingliang Wu
Keyword(s):  
Potassium Channel ◽  
Scorpion Toxin ◽  
Scorpion Toxins ◽  
Toxin Binding ◽  
Channel Interaction ◽  
Binding Interface ◽  
Α Helix ◽  
Interaction Law ◽  
Binding Interfaces ◽  
Β Sheet

: The scorpion toxins are the largest potassium channel-blocking peptide family. The understanding of toxin binding interfaces is usually restricted by two classical binding interfaces: one is the toxin α-helix motif, the other is the antiparallel β-sheet motif. In this review, such traditional knowledge was updated by another two different binding interfaces: one is BmKTX toxin using the turn motif between the α-helix and antiparallel β-sheet domains as the binding interface, the other is Ts toxin using turn motif between the β-sheet in the N-terminal and α-helix domains as the binding interface. Their interaction analysis indicated that the scarce negatively charged residues in the scorpion toxins played a critical role in orientating the toxin binding interface. In view of the toxin negatively charged amino acids as “binding interface regulator”, the law of scorpion toxin-potassium channel interaction was proposed, that is, the polymorphism of negatively charged residue distribution determines the diversity of toxin binding interfaces. Such law was used to develop scorpion toxin-potassium channel recognition control technique. According to this technique, three Kv1.3 channel-targeted peptides, using BmKTX as the template, were designed with the distinct binding interfaces from that of BmKTX through modulating the distribution of toxin negatively charged residues. In view of the potassium channel as the common targets of different animal toxins, the proposed law was also shown to helpfully orientate the binding interfaces of other animal toxins. Clearly, the toxin-potassium channel interaction law would strongly accelerate the research and development of different potassium channelblocking animal toxins in the future.

scholarly journals Secondary structure and biophysical activity of synthetic analogues of the pulmonary surfactant polypeptide SP-C

1995 ◽  
Vol 307 (2) ◽  
pp. 535-541 ◽  
Author(s):  
J Johansson ◽  
G Nilsson ◽  
R Strömberg ◽  
B Robertson ◽  
H Jörnvall ◽  
...  
Keyword(s):  
Secondary Structure ◽  
Pulmonary Surfactant ◽  
Transmembrane Helix ◽  
Helical Structure ◽  
Helical Conformation ◽  
Synthetic Analogues ◽  
Charged Amino Acids ◽  
Phospholipid Micelles ◽  
Helical Content ◽  
Biophysical Activity

Native pulmonary-surfactant-associated lipopolypeptide SP-C, its chemically depalmitoylated form and several synthetic analogues lacking the palmitoylcysteine residues were analysed for secondary structure in phospholipid micelles and for biophysical activity in 1,2-dipalmitoyl-sn-glycero-3- phosphocholine/phosphatidylglycerol/palmitic acid (68:22:9, by wt.). Compared with the native molecule, with the entire poly-valyl part in a known alpha-helical conformation, depalmitoylated SP-C was found to be still mainly alpha-helical, but with an approx. 20% decrease in the helical content. A synthetic hybrid polypeptide where the entire poly-valyl alpha-helical part of native SP-C had been replaced with the amino acid sequence of a transmembrane helix of bacteriorhodopsin is also predominantly alpha-helical. In contrast, synthetic SP-C analogues lacking only the palmitoyl groups, by replacement of the palmitoylcysteine residues with cysteine, phenylalanine or serine, or lacking the positively charged amino acids by replacement with alanine, are considerably less alpha-helical than both native and depalmitoylated SP-C. The data indicate that the SP-C palmitoyl groups are important for maintenance of the alpha-helical conformation in parts of the polypeptide, and that the poly-valyl alpha-helical conformation is not fully formed in synthetic SP-C polypeptides. Furthermore, the helical structure of both native and depalmitoylated SP-C in dodecylphosphocholine micelles is very resistant to thermal denaturation, exhibiting ordered structure at 90 degrees C. The alpha-helical content grossly parallels the peptide-induced acceleration of the spreading of phospholipids at an air/water interface and the increase of surface pressure. The data suggest that the alpha-helical conformation itself, rather than just the covalent structure, is of prime importance for the biological function of synthetic pulmonary-surfactant peptides.

Implications of an improved model of the TSH receptor transmembrane domain (TSHR-TMD -TRIO)

Endocrinology ◽  
2021 ◽  
Author(s):  
Mihaly Mezei ◽  
Rauf Latif ◽  
Bhaskar Das ◽  
Terry F Davies
Keyword(s):  
Small Molecules ◽  
Transmembrane Domain ◽  
Water Layer ◽  
Tsh Receptor ◽  
Transmembrane Helices ◽  
Transmembrane Region ◽  
Significant Preference ◽  
Group A ◽  
Improved Model ◽  
Intracellular Loops

Abstract The TSH receptor is a GPCR Group A family member with seven transmembrane helices. We generated three new models of its entire transmembrane region using a 600 ns molecular simulation. The simulation started from our previously published model which we have now revised by also modeling the intracellular loops and the C-terminal tail, adding internal waters and embedding it into a lipid bilayer with a water layer and with ions added to complete the system. We have named this model TSHR-TMD – TRIO since three representative dominant structures were then extracted from the simulation trajectory and compared with the original model. These structures each showed small but significant changes in the relative positions of the helices. The three models were also used as targets to dock a set of small molecules that are known active compounds including a new TSHR antagonist (BT362), which confirmed the appropriateness of the model with some small molecules showing significant preference for one or other of the structures.

Use of synchrotron-based FTIR microspectroscopy to determine protein secondary structures of raw and heat-treated brown and golden flaxseeds: A novel approach

2005 ◽  
Vol 85 (4) ◽  
pp. 437-448 ◽  
Author(s):  
P. Yu ◽  
J. J. McKinnon ◽  
H. W. Soita ◽  
C. R. Christensen ◽  
D. A. Christensen
Keyword(s):  
Secondary Structure ◽  
Matrix Protein ◽  
Protein Secondary Structure ◽  
Secondary Structures ◽  
Heat Processing ◽  
Lower Percentage ◽  
Protein Secondary Structures ◽  
Novel Approach ◽  
Α Helix ◽  
Β Sheet

The objectives of the study were to use synchrotron Fourier transform infrared microspectroscopy (S-FTIR) as a novel approach to: (1) reveal ultra-structural chemical features of protein secondary structures of flaxseed tissues affected by variety (golden and brown) and heat processing (raw and roasted), and (2) quantify protein secondary structures using Gaussian and Lorentzian methods of multi-component peak modeling. By using multi-component peak modeling at protein amide I region of 1700–1620 cm-1, the results showed that the golden flaxseed contained relatively higher percentage of α-helix (47.1 vs. 36.9%), lower percentage of β-sheet (37.2 vs. 46.3%) and higher (P < 0.05) ratio of α-helix to β-sheet than the brown flaxseed (1.3 vs. 0.8). The roasting reduced (P < 0.05) percentage of α-helix (from 47.1 to 36.1%), increased percentage of β-sheet (from 37.2 to 49.8%) and reduced α-helix to β-sheet ratio (1.3 to 0.7) of the golden flaxseed tissues. However, the roasting did not affect percentage and ratio of α-helix and β-sheet in the brown flaxseed tissue. No significant differences were found in quantification of protein secondary structures between Gaussian and Lorentzian methods. These results demonstrate the potential of highly spatially resolved S-FTIR to localize relatively pure protein in the tissue and reveal protein secondary structures at a cellular level. The results indicated relative differences in protein secondary structures between flaxseed varieties and differences in sensitivities of protein secondary structure to the heat processing. Further study is needed to understand the relationship between protein secondary structure and protein digestion and utilization of flaxseed and to investigate whether the changes in the relative amounts of protein secondary structures are primarily responsible for differences in protein availability. Key words: Synchrotron, FTIR microspectrosopy, flaxseeds, intrinsic structural matrix, protein secondary structures, protein nutritive value

scholarly journals Two-Dimensional Infrared Spectroscopy of Antiparallel β-Sheet Secondary Structure

2004 ◽  
Vol 126 (25) ◽  
pp. 7981-7990 ◽  
Author(s):  
Nurettin Demirdöven ◽  
Christopher M. Cheatum ◽  
Hoi Sung Chung ◽  
Munira Khalil ◽  
Jasper Knoester ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Secondary Structure ◽  
Two Dimensional ◽  
Two Dimensional Infrared Spectroscopy ◽  
Β Sheet
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