N-terminal amino acid residue

FIGURE 5.19 N-Tertninal analysis using Edman s reagent, phenylisothiocyanate. Phenylisothiocyanate combines with the N-terminus of a peptide under mildly alkaline conditions to form a phenylthiocarbamoyl substitution. Upon treatment with TFA (trifluo-roacetic acid), this cyclizes to release the N-terminal amino acid residue as a thiazolinone derivative, but the other peptide bonds are not hydrolyzed. Organic extraction and treatment with aqueous acid yield the N-terminal amino acid as a phenylthiohydantoin (PTH) derivative. 

In the spectrum of fully reductively [ C] methylated glycophorin A, the resonance at 42.8 p.p.m. must correspond to the N, N -di[ C]methylated, N-terminal amino acid residue. The ratio of the integrated intensities of the N, N -di[ C]methylLeu resonance to the N, N -di[ C]methyllysine resonances is 5 1, as expected. The integration values determined were valid, because the recycle times of spectra in Figs. 3B, 3C, and 3D were twice the spin-lattice relaxation-times (Tj values) of those of the di[ C]methyl carbon atoms, and also because the n.O.e. values of the N, N -di[ C]methyl and N, N -di[ C]methyl carbon atoms were equivalent. ... 

The possible role that the lysine residues, N-terminal amino acid residues, and carbohydrate residues may play in the display of the MN blood-group determinants by glycophorins A, A, and has been investigated. Assuming that the N-terminal amino acid in each of these glycoproteins plays a prominent role in the display of the MN blood-group determinant, labels were placed on the N-terminal amino acid residues of the glycoproteins. 

There are a number of studies that need to be made in order to provide further information about the structure of the N-terminal amino acid residues. One crucial set of experiments revolves around determination of the exact structure of the minor component observed in reductively... 

The amino group of the N-terminal amino acid residue of a peptide will react with the FDNB reagent to form the characteristic yellow DNP derivative, which may be released from the peptide by either acid or enzymic hydrolysis of the peptide bond and subsequently identified. This is of historic interest because Dr F. Sanger first used this reaction in his work on the determination of the primary structure of the polypeptide hormone insulin and the reagent is often referred to as Sanger s reagent. 

Which of the following reagents (when used under appropriate conditions) react with an N-terminal amino acid residue ... 

There are no special requirements in the selection of an N-terminal amino acid residue in a segment with which the carboxy component of a segment is to be coupled, unless a highly hindered amino acid or a secondary amino acid is selected. If a Pro or Hyp residue is located at the N-terminus of the segment, monitoring of the coupling reaction with ninhydrin or fluorescamine is extremely difficult. 

Scheme 25 Methylation of N-Terminal Amino Acid Residues on Solid Phase by the Mbh Method 1401...

Whilst metal-N(peptide) bond formation inhibits hydrolysis of the peptide bond, coordination to O(peptide) has the opposite effect. These differences in reactivity can be readily demonstrated and put to practical use with the inert Co111 complexes. One of the first examples was the reaction of [Co(trien)(H20)(OH)]2+ with peptides to give hydrolysis of the peptide bond at the N-terminal end. The proposed mechanism involving nucleophilic attack by hydroxide at the peptide carbon is shown in Scheme 7.110 Similar selective hydrolyses of N-terminal peptide bonds have since been demonstrated with other Co111 amine complexes and the reaction has been examined as a method for determining the N-terminal amino acid residue in peptides and proteins.1"112... 

To localize ERp on paraffin sections, 65-kDa antirat ER antibodies are used (Upstate Biotechnology, Lake Placid, NY). This antibody is obtained by immunizing rabbits with synthetic peptides representing the N-terminal amino acid residues 46-63 of human ER(3. The deparaffinized sections on slides are placed in the Target Retrieval Solution (pH 6.1)... 

The polypeptide structure is comprised of an N-terminal amino acid residue, a C-terminal residue and intervening amino acid residues, all of these being successively linked by peptide bonds. A critical property of the peptide bond (CO-NH) is that it has considerable double bond character (i.e. -CIO =NH+-) and accordingly no rotation occurs around this bond between the keto C and the amide N. 

Courts A (1954) The N-terminal amino acid residues of gelatin. 2. Themal degradation. Biochem J 58(l) 74-79... 

Because cobalt(III) complexes bind to the N-terminal amino acid residue of peptides, only the N-terminal peptide bond is hydrolyzed. It would be advantageous if the metal complex could coordinate to various parts of a peptide chain, thus allowing for cleavage of other areas of the peptide chain. Recently this has become an active area of research, and there have been several publications on the cleavage of the polypeptide backbone of proteins promoted by metal complexes. The advantage that these complexes have over the cobalt(III) complexes is that they can be selectively introduced on to various amino acid side chains, allowing for cleavage of peptide bonds at locations other than the N-terminus. This is of interest because,... 

V3. Van Vunakis, H., and Herriott, R., Structural changes associated with the conversion of pepsinogen to pepsin, I. The N-terminal amino acid residue and amino acid composition of the pepsin inhibitor. Biochim. Biophys. Acta 22, 537-543 (1956). 

A convenient way of representing peptide structures by use of standard abbreviations (see Table 36.1) is illustrated here. According to convention, the N-terminal amino acid residue (having the free amino group) is written at the left end, and the C-terminal amino acid residue (having the free carboxyl group) at the right end. 

N-terminal amino acid residue See amino acid... 

A cyclic, internal amide derivative of glutamic acid is pyrrolidone carboxylic acid (also known as pyroglu-tamic acid or 2-oxoproline). Some proteins (e.g., heavy chains of immunoglobulins Chapter 35) and peptides (e.g., thyrotropin-releasing hormone Chapter 33) have py-roglutamic acid as their N-terminal amino acid residue. 

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