Melanocortins are regulatory peptides formed by post-translational processing of pro-opiomelanocortin. Melanocortin peptides have been suggested to perform a variety of physiological roles ranging from control of behavior, memory, neurotrophic properties, antipyretic and modulation of immune system, etc. Their binding sites have been found distributed in tissues ranging from lachrymal and submandibular glands, pancreas, adipose tissue, bladder, duodenum, spleen, brain, gonadal tissues and malignant melanoma tumors. Five melanocortin receptors (MC-R) have been characterized to date. These include melanocyte-specific receptor (MSH or MC1-R), corticoaderenal-specific ACTH receptor (MC2-R), melacortin-3 (MC3-R), melanocortin-4 (MC4-R) and melanocortin-5 receptor (MC5-R). MC3-R and MC4-R are distributed in brain whereas MC5-R has a broad distribution.

Melanocyte Stimulating Hormone Receptor (MSH-R), also called Melanotropin Receptor, or Melanocortin-1 Receptor (MC1-R), is a 315 amino acid transmembrane protein belonging to the family of G-Protein coupled receptors. It is a receptor for MSH (a,b,g) and ACTH. Its activity is mediated by G-proteins, which activate adenylate cyclase. It is found in Melanocytes and corticoderenal tissue as well as various tissues like adrenal gland, leukocytes, lung, lymph node, ovary, testis, pituitary, placenta, spleen and uterus. Melanocortin-2 receptor (MC2-R) also called Aderenocorticotropic hormone receptor (ACTH-R) is a 297 amino acid transmembrane protein found in melanocytes and the corticoadrenal tissue. It mediates the corticotrophic effect of ACTH. Melanocortin-3 receptor (MC3-R) is expressed in brain. In humans it is a 360 AA protein whereas in mice and rats its 323 AA. MC4-R is a 332 amino acid transmembrane protein and is expressed in brain, placental and gut tissues. MC5-R is a 325 amino acid transmembrane protein expressed in the adrenals, stomach, lung and spleen and very low levels in the brain. It is also expressed in the three layers of adrenal cortex, predominantly in the aldosterone-producing zona glomerulosa cells.

ADI has produced rabbit-anti-melanocortin receptor antibodies using specific peptide sequences. Rabbit anti-Mouse MC1-R antibodies were raised against a 21 mer peptide from the 3rd cytoplasmic domain of the murine MC1-R. It shows strong homology to the Human, Bovine, Equine, and Sheep MCR1. Rabbit Anti-Mouse MC2-R antibodies were generated against a 17-mer peptide from the 4th cytoplasmic domain of the murine MCR2. It shows 85% homology to human MC2-R, 76% homology to golden hamster MC2-R, and 70% to bovine MC2-R. Anti-Human MC3-R antibodies (MCR31-S, antibody #1) have been raised to a 18 amino acid peptide sequence (designated MCR31-P) within the first extracellular domain of human MC3-R, and to a 18-mer peptide (antibody # 2) in the 3rd cytoplasmic domain (designated MCR32-P) of mouse MC3-R. MCR31-P has 100% homology to human MC3-R and 66% to mouse MC3-R. MCR32-P has 100% homology to mouse and 83% homology to rat and human MC3-R. Anti-Rat MC4-R antibodies were raised to an 18-mer peptide (designated MCR41-P) from the 1st extracellular domain of rat MC4-R. The mouse MCR41-P has 100% homology to rat and 88% homology to human MCR4. Antibody # 2 to the human MC4-R was raised to a 14 aa peptide (designated MCR42-P) within the 4th cytoplasmic loop of human MC4-R. MCR42-P has 64% homology to rat MC4-R. Anti-Mouse MC5-R was raised against a 15 amino acid peptide (MCR51-P), which maps to the 2nd extracellular domain of mouse MCR-5. The MCR51-P peptide has strong (93%) homology with human and rat, and 73% with bovine and hamster MC5-R. All peptides were specific for a given receptor and no significant homology was evident with other isoforms.

The control peptides were used to affinity purify antibodies. The antibody cross-reactivity of MCR antibodies amongst all species is not known. The appropriate control immunogenic peptides are available to confirm specificity of antibodies. Because of their very low mol. Wt, control peptides are not recommended for Western blotting.

M= Mouse; R=Rat; H=Human; Ha=Hamster; Rb=Rabbit; B=Bovine; C=Chicken; CT= near C-terminus; NT=near N-terminus; Internal=Middle of protein. EC=Extracellular; CP=Cytoplasmic

Control peptides, because of their small size, are not recommended for Western. They should be used in ELISA, dot blot or in antibody blocking studies. "Neat Antiserum" (unpurified crude antiserum) is suitable for ELISA and Western, whereas we recommend using "Affinity pure"(purified over the antigen columns) antibodies for Immunohistochemical applications.

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