A-Melanotropin

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.)... 

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

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... 

Alkylammonium acetate buffer systems have also attracted limited attention for the separation of tryptic digests of proteins on octadecyl silica 60). The ammonium formate or trifluoroacetate buffers have also been used in the reversed-phase HPLC separation of the tryptic, chymotryptic, and carboxypeptidase A digests 136) of a-melanotropin and its N,0-diacetylserine analog as well as for enzymatic digests of the adrenocorticotropic family 137). Ammonium bicarbonate eluent systems have proved useful in mapping studies due to the eluent s volatility and differ-... 

Glembotski, C. C. (1986). The characterization of the ascorbic acid-mediated a-amidation of a-melanotropin in cultured intermediate pituitary lobe cells. Endocrinology 118,1461-1468. 

Peptide synthesis. Hydrazine acetate is an effective reagent for cleaving protective N-phthaloyl groups in a neutral medium and hence can be used in the synthesis of alkali-sensitive peptides such as a-melanotropin. Tlius this substance... 

Proteins may be acetylated, usually on the a-amino group s TV-terminal residue but occasionally on the e-amino group of a lysine residue. Acetylation is effected with acetylcoenzyme A (8.3), although other biochemical acetylating agents are well known. a-Melanotropin or a-melanocyte-stimulating hormone (a-MSH) provides an example of post-translational acetylation ... 

Some polyproteins are differentially cleaved in different tissues. An example is proopiomelanocortin, a polyprotein that is the source of several hormones synthesized in the pituitary gland. In the anterior lobe of the pituitary, the polyprotein is cleaved to release -lipotropin and adrenocorticotropic hormone (ACTH). In the intermediate lobe, a different pattern of cleavage forms jS-endorphin and a-melanotropin (Chapter 31). 

Nystrom, A., Andersson, P.M. and Lundstedt, T. (2000) Multivariate data analysis of topographically modified a-melanotropin analogues using auto and cross auto covariances (ACC). Quant. Struct. -Act. Relat., 19, 264—269. 

Not long ago. an a-melanotropin peptide analogue, cyclized through " Tc coordination, was synthesized while retaining high affinity for receptors present on melanoma cells. In vivo the complex revealed selective accumulation in a murine melanoma tumor [246a],... 

Haynes, L. and Smith, M.E. (1985) Presence of immunoreac-tive a-melanotropin and /3-endorphin in spinal motoneu-rones of the dystrophic mouse. Neurosci. Lett. 58 13-18. 

Hughes, S. and Smith, M.E. (1988) Effect of nerve section on /3-endorphin and a-melanotropin immunoreactivity in motor nerves of normal and dystrophic mice. Neurosci. Lett. 92 1-7. 

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