Peptide, amino acid sequence cysteine-containing

In contrast to Gram-negatives, many Gram-positive bacteria employ post-translationally modified peptides processed from larger precursors as QS signal molecules. In Staphylococcus aureus, for example, a family of peptide (7-9 amino acid residues) thiolactones which vary in the primary amino acid sequence but contain a conserved cysteine at position 5 control the expression of cell wall colonization factors and exotoxins [24-26]. 

Since aromatic amino acids and cysteine are absent, there is no protein absorption above 270 nm. Metallothioneins exhibit a broad absorption peak, with the maximum at 190 mn. Absorptions due to the metal-thiolate complexes show as shoulders at 250 nm (Cd), 220 nm (Zn) and 270 nm (Cu).1458,1459 Theoretical predictions based on the amino acid sequence of the peptide chain indicate that the or-helical conformation is forbidden, and /3-structure is almost impossible to attain. CD and NMR studies on both the metal-containing and metal-free protein confirmed the predictions.1459 1460 However, metallothioneins are stable to tryptic digestion and the slow exchange of many peptide hydrogens of metallothionein with those of the solvent suggest that the protein has a compact and well-defined tertiary structure. 

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... 

The amino acid sequence of a fragment containing a reactive cysteine residue was reported by Harris (86) and, later, that of another peptide containing a second cysteine residue by Twu et al. (406,407). The absence of a free N-terminus in the protein was demonstrated in other studies (378,404) and subsequently found to be resulting from blockage by an acyl group (1-2). Tryptic peptides of the enzyme were partly characterized by Butler et al. (378,379). 

Trefoil peptides constitute a rapidly growing family of peptides containing one or more characteristic trefoil domains. A trefoil domain is defined as a sequence of 38 or 39 amino acid residues in which 6 cysteine residues are disulfide-linked in the configuration 1-5, 1-A, and 3-6 when the cysteines are numbered from the N-terminal end of the peptide. The amino acid sequence together with the disulfide bonds thus forms a distinctive three-leafed structure giving the peptide family its name. 

Modified peptides are being defined as peptides in which in essence the amino acid sequence is unchanged but the peptide contains e. g. some unnatural amino acids, a modification of a cysteine residue or a phospho amino acid. Peptidomimetics are compounds which imitate the structure and/or imitate or block the biological effect of a peptide at the receptor level [2a]. As a consequence peptidomimetics span the whole range of compounds varying from peptide isosteres to compounds without an identifiable amino acid or peptide moiety.,... 

Defensins have also been isolated from a variety of insect species (34,35). They share an array of six cysteine residues resulting in a tertiary structure containing three disulfide bridges but forming a structure that is distinct from mammalian defensins (42). These peptides instead share amino acid sequence homology and tertiary structure homoh ogy with royalisin from bees and charybdotoxin and defensin from scorpions (43- 5). 

A scientist has constructed a secret peptide to carry a message. You know onl> the composition of the peptide, which is six amino acids long. It contains one serine S, one threonine T, one cysteine C, one arginine R, and two glutamates E. What is the probability that the sequence SECRET will occur by chance ... 

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