Melanotropins

Melanotropin. [9034-42-8] (18-22 amino acids peptide), amorphous. Extract separated by ion-exchange on carboxymethyl cellulose, desalted, evapd and lyophilised, then chromatographed on Sephadex G-25. [Lande et al. Biochem Prep 13 45 1971.]... 

FIGURE 11.8 Isocratic elution separations of 20pg (panel A) and 10mg (panel B) of a melanotropin mixture. Column 4.6 x 250 mm ODS Eluent 0.25% formic acid, 0.5% triethylamine, 24% acetonitrile in water. Components 1, unknown 2, MSH sulfoxide 3, acetyl-MSH sulfoxide 4, MSH 5, acetyl-MSH. (Reprinted with permission from Elsevier from Barnthouse, K.A. et al., J. BiotechnoL, 66, 125, 1998. Copyright.)... 

Of particular interest in the case of the displacement separation of the melanotropins, acetonitrile was mixed with both the carrier and the displacer. The purpose was to suppress the sigmoidal isotherm of MSH which was then found to underlie the Langmuirian isotherm of the displacer in the area of operational interest. The idea of isotherm suppression through use of acetonitrile/displacer mixtures surfaced again later in the Horvath laboratory (see below). 

Table IV Relative Potency and Prolongation of Selected a-Melanotropin Analogs in the In Vitro Frog and Lizard Systems ...

Dithiol melanotropin peptide cyclized via rhenium metal coordination PDB ID IBOQ... 

GPCR 3D structural models for neurotensin and oc-melanotropin agonists... 

The anterior lobe of the pituitary secretes a series of ten or more peptide hormones ranging in size from the 20-residue (i-melanotropin to the 200-residue growth hormone (somatotropin). Several of these contain a common heptapeptide unit, which is marked in green in the following structure ... 

Not only this heptapeptide but also the entire amino acid sequence of a-melanotropin is found within the sequence of corticotropin (Fig. 30-2), which has an additional 29 amino acids at the C-terminal end.25 The same heptapeptide was also found in the lipotropins. The explanation is, in part, that several of these hormones arise from a single 31-kDa precursor protein called prepro-opiomelanocortin.25 26 It contains an N-terminal signal sequence that is removed shortly after synthesis, as well as pairs of adjacent basic residues (Arg-Arg, Arg-Lys, Lys-Arg and Lys-Lys) at a number of places (Fig. 30-2). After removal of the... 

Corticotropin-Releasing Hormone (CRH or CRF) Melanotropin-Releasing Hormone (MRH) ... 

The N-terminal cyclic hexapeptide of oxytocin and the C-terminal tripeptide of oxytocin were isolated from hypothalami respectively as MRH 41 and melanotropin release-inhibiting hormone 42 (MIH) 5). 

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