Oxytocin amino acid sequence

Fig. 1. Stmcture of oxytocin and arginine vasopressin. Numbers indicate approximate location of amino acids sequences found in Table 1. A, oxytocin B,...

What is the amino acid sequence of reduced oxytocin What is the structure of oxytocin itself ... 

Vasopressin/Oxytocin. Figure 1 Amino acid sequence of AVP and OT. The disulphide bridge between Cys 1 and Cys 6 is shown. 

Oxytocin is a 9-amino-acid peptide with an intrapeptide disulfide cross-link (Figure 37-5). Its amino acid sequence differs from that of vasopressin at positions 3 and 8. 

The amino acid sequences in (a) oxytocin and (b) vasopressin. The differing amino acids are boxed. 

Manning M. Synthesis by the Merrifield method of a protected nonapeptide amide with the amino acid sequence of oxytocin. J. 

As we saw in the case of vasopressin and oxytocin (Section 9.4), small changes in amino acid sequence can cause profound differences in the functioning of proteins. For example, a minor change in sequence in the blood protein hemoglobin causes the fatal sickle-cell disease. 

H. Tuppy, Amino acid sequence in oxytocin. Biochim. Biophys. Acta 11 449-450 (1953) also H. Tuppy, H. Michl, Uber die chemische Struktur des Oxytocins. Monatshefte der Chemie 84 1011-1020(1953)... 

In 1953 a significant achievement was reported from the same university the elucidation of the structure of oxytocin by Hans Tuppy. Tuppy had just returned from Cambridge, England, where, as one of the principal coworkers of Sanger, he determined the amino acid sequence of the B-chain of insulin. In Vienna, almost singlehandedly and with the simplest means, he solved the sequence of oxytocin and published it a few months ahead of V. du Vigneaud (cf. p. 140). From Tuppy s associates H. Nesvadba, first at the University later at the SANDOZ laboratories in Vienna, studied problems of peptide synthesis. 

Amino acid sequences of oxytocin and vasopressin. The difference in oniy two amino acids (shown in red) in these two compounds resuits in very different physioiogicai activity. The C-terminai amino acid has an amide structure (Giy-NH2) instead of -COOH. 

All the pieces of the formulas of both oxytocin and vasopressin fell into place when, in 1953, several laboratories independently published the complete amino acid sequence of both these hormones. It thus became obvious that each of them contained a 20-member disulfide ring and tripeptide side chain. Oxytocins obtained from man, beef, hog, horse, sheep, and... 

Oxytocin and vasopressin (Fig. 24.6) are two rather small polypeptides with strikingly similar structures (where oxytocin has leucine, vasopressin has arginine, and where oxytocin has isoleucine, vasopressin has phenylalanine). In spite of the similarity of their amino acid sequences, these two polypeptides have quite different physiological effects. Oxytocin occurs only in the female of a species and stimulates uterine contractions during childbirth. Vasopressin occurs in males and females it causes contraction of peripheral blood vessels... 

Several human receptors for the neurohypophyseal hormones have been cloned and the sequences elucidated. The human V2 receptor for antidiuretic hormone presumably contains 371 amino acids and seven transmembrane segments and activates cycHc AMP (76). The oxytocin receptor is a classic G-protein-coupled type of receptor with a proposed membrane topography also involving seven transmembrane components (84). A schematic representation of the oxytocin receptor stmcture within the membrane is shown in Eigure 4 (85). 

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