Question

This is BIOchemistry) For the appetite-related signaling molecule MELANOCORTIN:

a.) What is the specific function of that molecule?

b.) What is the mechanism of that action (how does it do what it does)?

c.) How is that molecule made? Describe any prepro- and pro- forms and associated cleavages or covalent bonds or phosphorylations associated with the molecule.

d.) Describe how the molecule is regulated

(This problem relates to chapters 22, Biosynthesis of amino acids, nucleotides, and related molecules; and chapter 23, hormonal regulation and integration of mammalian metabolism, from the Lehninger Biochemistry textbook).

Answer 1

Melanocortin:

Melanocortin are group of peptide hormones which consists of ACTH(adrenocorticotropic hormone) and different forms of melanocyte stimulating hormone (MSH) and these are derived from proopiomelanocortin(POMC) in the pituitary gland.

a.) Specific function of melanocortin molecule:

Melanocortin receptor is the melanocyte alpha-msh receptor which is expressed on cutaneous melanocytes.

It plays a key role which determines skin and hair pigmentation. It is the main function.

Melanocortin MC4 receptor which is expressed as predominantly in CNS( central nervous system) and which helps in regulation of both intake of food and sexual function.

The melanocortin receptors and function is as follows:

MC1R - yellow- red and black brown pigment regulation

MC2R- steroidogenesis.

b.) Mechanism of melanocortin molecule:

These are series of potent neuropeptides which are derived from POMC(parent propopiomelanocortin molecule).

These are expessed predominantly in brain, specifically the pituitary gland and CNS (central nervous system).

The existence of regulatory functions which is outside of brain is in a wide range of peripheral tissues.

Many important melanocortin peptides which are different in function are formed by tissue specific proteolytic clevage of POMC, which help in generating peptides including ACTH.

Alpha-MSH has a very significant role which helps in Controlling inflammation and immodulation and it has also have control over energy homeostasis and secretion of exocrine and control of sexual behaviour.

These melanocortin system and receptors have the focus of key signalling mechanism of Alpha-MSH and link of receptor through to function.

c.) Composition of Melanocortin:(Molecule made):

Melanocortin are group of peptide hormones which consists of ACTH( adrenocorticotropic hormone) and different forms of MSH( melanocyte-stimulating hormone) and these are derived from POMC(proopiomelanocortin) which is in pituitary gland.

Adrenocorticotropic hormone (ACTH) which is also known as adrenocorticotropin, corticotropin) which is a polypeptide tropic hormone which is produced and secreted by anterior pituitary gland.

*It is pro-opiomelanocortin.

MSH(melanocyte stimulating hormone) which is also known as melanotropins or intermedins.

* It is a pro-opiomelanocortin.

POMC(proopiomelanocortin) which is a precursor polypeptide with 241 amino acid residues and is synthesized by 285 amino acid long polypeptide precursor pre-pro-opiomelanocortin (pre-POMC) which is done by removing of 44 amino acid long peptide sequence which is done during translation in the pituitary.

d.) Regulation of Melanocortin molecule:

The melanocortin is regulated by pituitary gland indirectly by releasing the proopiomelanocortins that is ACTH and MSH.