Peptide, amino acid sequence histidine-containing

In addition to the last example, in which H-Hg couplings were measured, 199Hg NMR has been used to investigate the solution structure of Hg11 complexes of oligopeptides containing cysteine and histidine residues. In this work it was shown that the magnitude of the chemical shift is dependent upon the amino acid sequence of the peptide (Adachi et al., 1992). 

Jornvall and Harris (91) presented data for the structures around all of the 14 cysteine residues in each protein chain. Analysis by Jornvall (92,93) of different peptide mixtures obtained after treatment of the protein with trypsin (before or after maleylation), chymotrypsin, pepsin, cyanogen bromide, or thermolysin yielded amino acid sequence information for all parts of the subunit and the primary structure of the whole protein chain was deduced (5S). It was found to contain 374 residues and is shown in Table I. An acetylated serine residue is at the N-terminus and the reactive cysteine residue is at position 46. Some residues are unevenly distributed (PS). Six of the seven histidine residues are in the N-terminal half of the molecule, the two tryptophan residues are in either terminal region, the four tyrosine residues are in the middle of the primary structure, and none of the 14 cysteine residues occur in the C-terminal quarter of the molecule. A characteristic distribution of hydrophobic residues was also noticed (93), which may now be partly correlated with the presence of large hydrophobic cores in the tertiary structure of the protein (Section II,C,3). Most regions of the primary structure were analyzed in many different overlapping peptides (92-9 ) with a corresponding increase in reliability. The structure is in excellent agreement with the total composition determined by acid hydrolysis (93). It is compatible with independently determined partial structures of... 

Nisin belongs to a group of bactericidal peptides called type A lantibiotics (Willey and van der Donk, 2007). Four natural nisin variants (A, Z, Q, and U) have been discovered. Nisins A, Z, and Q are produced by L. lactis while nisin U is produced by Streptococcus uberis. Two main variants of nisin A and Z have been described (De Vuyst and Vandamme, 1994). Nisin Z is widely distributed and contains asparagine instead of histidine at position 27 of the amino acid sequence of nisin A (Fig. 11.2). The two variants have nearly equal bactericidal activity, membrane insertion, and pore-forming ability. 

In recent years, there has been a lot of interest in the binding of zinc(II) by the peptide sequence (Tyr, Phe)-X s X2,4-Cys-Xs Phe Xj Leu His Xs,4 His where X is a relatively variable amino acid. This peptide sequence has been termed a Zinc Finger. The zinc ion is coordinated tetrahedrally by the two cysteine and histidine residues. Proteins that contain these sequences have been shown to bind to specific sites on nucleic acids (see Zinc DNA-binding Proteins). 

Several other operons for the biosynthesis of amino acids in E. coli also are regulated by attenuator sites. The leader peptide of each contains an abundance of the amino acid residues of the type synthesized by the operon (Figure 31.35). For example, the leader peptide for the phenylalanine operon includes 7 phenylalanine residues among 1 5 residues. The threonine operon encodes enzymes required for the synthesis of both threonine and isoleucine the leader peptide contains 8 threonine and 4 isoleucine residues in a 16-residue sequence. The leader peptide for the histidine operon includes 7 histidine residues in a row. In each case, low levels of the corresponding charged tRNA causes the ribosome to stall, trapping the na.scent mRNA in a state that can form a structure that allows RNA polymerase to read through the attenuator site. 

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