scholarly journals o-Quinones formed in plant extracts. Their reactions with amino acids and peptides

1969 ◽  
Vol 112 (5) ◽  
pp. 609-616 ◽  
Author(s):  
W. S. Pierpoint
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Plant Extracts ◽  
Thiol Group ◽  
Amino Group ◽  
Amino Groups ◽  
Terminal Amino Acid ◽  
Secondary Reactions ◽  
Terminal Amino ◽  
Group 5

1. The reactions of amino acids and peptides with the o-quinones produced by the enzymic oxidation of chlorogenic acid and caffeic acid have been studied manometrically and spectrophotometrically. 2. Amino acids, except lysine and cysteine, react primarily through their α-amino groups to give red or brown products. These reactions, which compete with the polymerization of the quinones, are followed by secondary reactions that may absorb oxygen and give products with other colours. 3. The ∈-amino group of lysine reacts with the o-quinones in a similar way. The thiol group of cysteine reacts with the quinones, without absorbing oxygen, giving colourless products. 4. Peptides containing cysteine react with the o-quinones through their thiol group. 5. Other peptides, such as glycyl-leucine and leucylglycine, react primarily through their α-amino group and the overall reaction resembles that of the N-terminal amino acid except that it is quicker. 6. With some peptides, the secondary reactions differ from those that occur between the o-quinones and the N-terminal amino acids. The colours produced from carnosine resemble those produced from histidine rather than those from β-alanine, and the reactions of prolylalanine with o-quinones are more complex than those of proline.

Studies on Nα-acylated proteins: The N-terminal sequences of two muscle enolases

1985 ◽  
Vol 5 (10-11) ◽  
pp. 847-854 ◽  
Author(s):  
Christopher C. Q. Chin ◽  
Finn Wold
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Ion Exchange ◽  
Coho Salmon ◽  
Standard Procedure ◽  
Exchange Chromatography ◽  
Rabbit Muscle ◽  
Terminal Amino Acid ◽  
Terminal Amino ◽  
Acylated Proteins

A standard procedure for the identification of the N-terminal amino acid in Nα-acylated proteins has been developed. After exhaustive proteolysis, the amino acids with blocked α-amino groups are separated from positively charged, free amino acids by ion exchange chromatography and subjected to digestion with acylase I. Amino acid analysis before and after the acylase treatment identifies the blocked N-terminal amino acid. A survey of acylamino acid substrates showed that acytase will liberate all the common amino acids except Asp, Cys or Pro from their N-acetyl- and N-butyryl derivatives, and will also catalyze the hydrolysis of N-formyl-Met and N-myristyl-Val. Thus, the procedure cannot identify acylated Asp, Cys or Pro, nor, because of the ion exchange step, Nα-acyl-derivatives of Arg, Lys or His. Whenever the protease treatment releases free acylamino acids, the remaining amino acids should be detected. When applied to several proteins, the procedure confirmed known N-terminal acylamino acids and identified acyl-Ser in enolases from chum and coho salmon muscle and in pyruvate kinase from rabbit muscle, and acyl-Thr in phosphofructokinase from rabbit muscle. The protease-acylase assay has been used to identify blocked peptides from CNBr- or protease-treated proteins. When such peptides were treated with 1n HCl at 110° for 10 min, sufficient yields of deacylated, mostly intact, peptide were obtained to permit direct automatic sequencing. The N-terminal sequences of rabbit muscle and coho salmon enolase were determined in this way and are compared to each other and to the sequence of yeast enolase.

scholarly journals Determination of Peptide Contact Points in the Human Angiotensin II Type I Receptor (AT1) with Photosensitive Analogs of Angiotensin II

1999 ◽  
Vol 13 (4) ◽  
pp. 578-586 ◽  
Author(s):  
Stéphane A. Laporte ◽  
Antony A. Boucard ◽  
Guy Servant ◽  
Gaétan Guillemette ◽  
Richard Leduc ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Angiotensin Ii ◽  
Transmembrane Domain ◽  
At1 Receptor ◽  
High Yield ◽  
Type I ◽  
Terminal Amino Acid ◽  
Contact Points ◽  
Terminal Amino

Abstract To identify ligand-binding domains of Angiotensin II (AngII) type 1 receptor (AT1), two different radiolabeled photoreactive AngII analogs were prepared by replacing either the first or the last amino acid of the octapeptide by p-benzoyl-l-phenylalanine (Bpa). High yield, specific labeling of the AT1 receptor was obtained with the 125I-[Sar1,Bpa8]AngII analog. Digestion of the covalent 125I-[Sar1,Bpa8]AngII-AT1 complex with V8 protease generated two major fragments of 15.8 kDa and 17.8 kDa, as determined by SDS-PAGE. Treatment of the[ Sar1,Bpa8]AngII-AT1 complex with cyanogen bromide produced a major fragment of 7.5 kDa which, upon further digestion with endoproteinase Lys-C, generated a fragment of 3.6 kDa. Since the 7.5-kDa fragment was sensitive to hydrolysis by 2-nitro-5-thiocyanobenzoic acid, we circumscribed the labeling site of 125I-[Sar1,Bpa8]AngII within amino acids 285 and 295 of the AT1 receptor. When the AT1 receptor was photolabeled with 125I-[Bpa1]AngII, a poor incorporation yield was obtained. Cleavage of the labeled receptor with endoproteinase Lys-C produced a glycopeptide of 31 kDa, which upon deglycosylation showed an apparent molecular mass of 7.5 kDa, delimiting the labeling site of 125I-[Bpa1]AngII within amino acids 147 and 199 of the AT1 receptor. CNBr digestion of the hAT1 I165M mutant receptor narrowed down the labeling site to the fragment 166–199. Taken together, these results indicate that the seventh transmembrane domain of the AT1 receptor interacts strongly with the C-terminal amino acid of[ Sar1, Bpa8]AngII, whereas the N-terminal amino acid of[ Bpa1]AngII interacts with the second extracellular loop of the AT1 receptor.

Nuclear Magnetic Resonance Studies of Phenylthiohydantoin Amino Acids

1975 ◽  
Vol 53 (9) ◽  
pp. 1005-1009 ◽  
Author(s):  
C. S. Tsai ◽  
N. L. Fraser ◽  
H. Avdovich ◽  
J. P. Farant
Keyword(s):  
Amino Acids ◽  
Nuclear Magnetic Resonance ◽  
Amino Acid ◽  
Magnetic Resonance ◽  
Diagnostic Purpose ◽  
Edman Degradation ◽  
Terminal Amino Acid ◽  
Magnetic Resonance Studies ◽  
Terminal Amino ◽  
Derivatives Of

Proton magnetic spectra of 3-phenyl-2-thiohydantoin derivatives of common amino acids in deuterated dimethyl sulfoxide were recorded. Spectral data pertaining to characteristic protons for diagnostic purpose were compiled. Their application to the N-terminal amino acid analysis of peptide by Edman degradation was examined.

scholarly journals Phosphorus (V) porphyrin diaxially substituted with Leu-enkephalin

2004 ◽  
Vol 2 (3) ◽  
pp. 446-455 ◽  
Author(s):  
Mariusz Gajewski ◽  
Leszek Czuchajowski
Keyword(s):  
Amino Acids ◽  
Photodynamic Therapy ◽  
Amino Acid ◽  
Biologically Active ◽  
Solution Phase ◽  
Terminal Amino Acid ◽  
Leucine Enkephalin ◽  
Potential Applications ◽  
Biologically Active Peptide ◽  
Terminal Amino

AbstractSynthesis of the first phosphorus (V) porphyrin-peptide conjugate was successfully accomplished. A biologically active peptide, leucine enkephalin, was constructed on the phosphorus atom of the 5,10,15,20-meso-tetraphenylporphinato dichlorophosphorus (V) chloride. The method involved solution phase peptide synthesis. The first C-terminal amino acid in the sequence of the peptide was axially attached to the porphyrin through a linker, 3-aminopropanol, and the remainder of leucine enkephalin was synthesized by subsequent additions of amino acids. Leucine enkephalin-P(V) porphyrin conjugate represents a new group of compounds, and its synthesis broadens potential applications of P(V) porphyrine, e.g. in photodynamic therapy.

scholarly journals Impact of C-terminal amino acid composition on protein expression in bacteria

2019 ◽  
Author(s):  
Marc Weber ◽  
Raul Burgos ◽  
Eva Yus ◽  
Jae-Seong Yang ◽  
Maria Lluch-Senar ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Protein Expression ◽  
Translation Termination ◽  
Terminal Sequence ◽  
Bacterial Taxonomy ◽  
Terminal Amino Acid ◽  
Protein Levels ◽  
Terminal Amino ◽  
The Impact

AbstractThe C-terminal sequence of a protein is involved in processes such as efficiency of translation termination and protein degradation. However, the general relationship between features of this C-terminal sequence and levels of protein expression remains unknown. Here, we identified C-terminal amino acid biases that are ubiquitous across the bacterial taxonomy (1582 genomes). We showed that the frequency is higher for positively charged amino acids (lysine, arginine) while hydrophobic amino acids and threonine are lower. In highly abundant proteins, the C-terminal residue is more conserved. We then studied the impact of C-terminal composition on protein levels in a library of M. pneumoniae mutants, covering all possible combinations of the two last codons. We found that charged and polar residues, in particular lysine, led to higher expression, while hydrophobic and aromatic residues led to lower expression, with a difference in protein levels up to 4-fold. Our results demonstrate that the identity of the last amino acids has a strong influence on protein expression levels and is under selective pressure in highly expressed proteins.

scholarly journals Helix capping propensities in peptides parallel those in proteins

1993 ◽  
Vol 90 (23) ◽  
pp. 11332-11336 ◽  
Author(s):  
A Chakrabartty ◽  
A J Doig ◽  
R L Baldwin
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rank Order ◽  
Alpha Helix ◽  
Asymmetric Distribution ◽  
Minor Effect ◽  
Terminal Amino Acid ◽  
Helix Stability ◽  
Acetyl Group ◽  
Terminal Amino

Helix content of peptides with various uncharged nonaromatic amino acids at either the N-terminal or C-terminal position has been determined. The choice of N-terminal amino acid has a major effect on helix stability: asparagine is the best, glycine is very good, and glutamine is the worst helix-stabilizing amino acid at this position. The rank order of helix stabilization parallels the frequencies of these amino acids at the N-terminal boundary (N-cap) position of helices in proteins found by Richardson and Richardson [Richardson, J. S. & Richardson, D. C. (1988) Science 240, 1648-1652], and the N-terminal amino acid in a peptide composed of helix-forming amino acids may be considered as the N-cap residue. The choice of C-terminal amino acid has only a minor effect on helix stability. N-capping interactions may be responsible for the asymmetric distribution of helix content within a given peptide found by various workers. An acetyl group on the N-terminal alpha-amino function cancels the N-cap effect and the acetyl group is equivalent to N-terminal asparagine in an unacetylated peptide. Our results demonstrate a close relationship between the mechanisms of alpha-helix formation in peptides and in proteins.

scholarly journals Human complement component C4. Structural studies on the fragments derived from C4b by cleavage with C3b inactivator

1981 ◽  
Vol 199 (2) ◽  
pp. 351-357 ◽  
Author(s):  
E M Press ◽  
J Gagnon
Keyword(s):  
Amino Acid ◽  
Thiol Group ◽  
Peptide Bond ◽  
Carbohydrate Content ◽  
Amino Acid Sequences ◽  
Terminal Amino Acid ◽  
Radioactive Label ◽  
Terminal Residue ◽  
Alpha Chain ◽  
Terminal Amino

1. One of the activation products of C4, C4b, was prepared, and the reactive thiol group on the alpha′-chain was radioactively labelled with iodo[2-14C]acetic acid. The alpha′-chain was isolated and the N-terminal amino acid sequence of the first 13 residues was determined. 2. C4b was cleaved by C3bINA in the presence of C4b-binding protein and C4d and C4c isolated. The radioactive label and therefore the reactive thiol group were located to C4d. 3. C4c was reduced and alkylated and the two alpha′-chain fragments of C4c were separated. 3. The molecular weights, amino acid analyses and carbohydrate content of the three alpha′-chain fragments were determined. C4d has a mol.wt. of 44500 and a carbohydrate content of 6%. The two alpha′-chain fragments of C4c have mol.wts. of 25000 (alpha 3) and 12000 (alpha 4) and carbohydrate contents of 10 and 22% respectively. 4. The N-terminal amino acid sequences of C4d, the alpha 3 and the alpha 4 fragments were determined for 18, 24 and 11 residues respectively and, by comparison with the N-terminal sequence of the C4b alpha′-chain, the 25000-mol.wt. fragment (alpha 3) was shown to be derived from the N-terminal part of the alpha′-chain. 5. C-Terminal analyses were done on the alpha′-chain and its three fragments. Arginine was found to be the C-terminal residue of C4d and of the alpha 3 fragment. The C-terminal residue of the alpha′-chain and of the alpha 4 fragment could not be identified. The order of the three fragments of the alpha′-chain is therefore: alpha 3(25000)--C4d(44500)--alpha 4(12000). The specificity of C3bINA is for an Arg--Xaa peptide bond.

Convergent peptide synthesis

1999 ◽  
Author(s):  
Kleomenis Barlos ◽  
Dimitrios Gatos
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Peptide Synthesis ◽  
Solid Phase ◽  
Peptide Chain ◽  
Chain Elongation ◽  
Peptide Fragments ◽  
Terminal Amino Acid ◽  
Convergent Synthesis ◽  
Terminal Amino

Besides the classical step-by-step synthesis, the convergent solid phase peptide synthesis (CSPPS) was developed for the preparation of complex and difficult peptides and small proteins. According to this method, suitably protected peptide fragments spanning the entire peptide sequence and prepared on the solid phase are condensed, either on a solid support or in solution, to the target peptide. Convergent synthesis is reviewed in recent publications. In this chapter, full experimental details are given for the preparation of complex peptides by applying convergent techniques, using 2-chlorotrityl chloride resin (CLTR) and Fmoc-amino acids. In the step-by-step peptide chain elongation the resin-bound C-terminal amino acid is reacted sequentially with suitably protected and activated amino acids. The peptide is thus elongated steadily towards the N-terminal direction. This is advantageous over the opposite direction where the elongation is performed from the N- to the C-terminus, because in the second case the growing peptide is activated at the C-terminal amino acid, which leads to its extensive racemization. This limits considerably the synthetic possibilities of the method. In convergent synthesis, no directional restrictions exist and the chain elongation can be performed with equal possibility to be successful to any direction. Figure 1 describes schematically the C- to N-terminal synthesis which is the most studied to date. The strategies where the synthesis begins from a central fragment and the peptide chain is extended to both C- and N-terminal directions and from the N-terminal towards the C-terminal can be considered, at the present time, to be in its infancy. In general, protected peptide fragments of any length can be used in the condensation reaction, if they are of satisfactory purity and solubility. Usually, fragments of up to 15 amino acids in length are used, because of their simpler purification by RP-HPLC compared with the longer peptides. The solubility of protected peptide acids is independent of their length. The selection of the correct fragments is very important for the success of convergent synthesis. It is helpful to analyse all available structural information, determined or calculated, for the target peptide. Peptide regions where β-turns are known to occur are readily identified as ‘difficult’ sequences during their synthesis.

N-TERMINAL AMINO ACIDS OF THE PROTEINS OF THE FLOATING FRACTION OF EGG YOLK

1958 ◽  
Vol 36 (9) ◽  
pp. 951-952 ◽  
Author(s):  
David B. Smith ◽  
K. J. Turner
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Primary Structure ◽  
Egg Yolk ◽  
Minor Components ◽  
Terminal Amino Acid ◽  
Hen’S Egg ◽  
Terminal Amino

Lysine is the major N-terminal amino acid of both the soluble and insoluble fractions of the floating lipoprotein of hen's egg yolk, which suggests a common primary structure. Several minor components are also present in both fractions.

Purification of the delta toxin of Staphylococcus aureus

1970 ◽  
Vol 16 (8) ◽  
pp. 703-708 ◽  
Author(s):  
J. D. Caird ◽  
G. M. Wiseman
Keyword(s):  
Amino Acids ◽  
Staphylococcus Aureus ◽  
Amino Acid ◽  
Ammonium Sulphate ◽  
Deae Cellulose ◽  
Aureus Strain ◽  
Terminal Amino Acid ◽  
Terminal Amino ◽  
Two Peaks

An improved procedure for the purification of the delta toxin of Staphylococcus aureus strain E-delta has been devised which relies upon precipitation at pH 4.0 and further treatment with ammonium sulphate. A final step consists of passage twice through a column of DEAE-cellulose. Toxin obtained by this method appeared to be homogeneous on the basis of immunodiffusion and electrophoresis studies. However, two peaks with sedimentation coefficients of 2.8 S and 9.8 S were obtained when toxin was examined in the ultracentrifuge. Proline was identified as the N-terminal amino acid. No other N-terminal amino acids were detected in the purified toxin.

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