title: Partial characterization of an abundant human skin melanosomal 66 kDa protein (MP 66) and investigation to purify a similar protein from B16 murine melanoma tumours.
abstract: A single polypeptide protein of molecular weight 66kDa (MP 66), purified to homogeneity from melanosomes of normal human cadaver skin epidermal melanocytes, was further characterized. Based on the yield in the present investigation, the intracellular concentration of this protein was calculated to be 4.2 microM. It was shown to be a glycoprotein on gel electrophoresis. Based on its partial N-terminal amino acid sequence, it was shown to be distinct from known melanosomal proteins such as gp 75, tyrosinase-related protein-2 (TRP-2) and Pmel 17. Investigation to purify a similar type of protein from B16 murine melanoma tumours by following the same purification procedure resulted in a partially purified protein with a molecular weight of 66 kDa. However, unlike MP 66, this protein did not show inhibition of the monophenolase activity of tyrosinase at pH 6.8. Finally, the effects of 0.5 mM each of CaCl2, ZnSO4 and FeSO4 together, and of human skin epidermal melanosomal proteins, were studied on melanin polymerization at pH 4.7. The metal cations failed to initiate melanin polymerization, while melanosomal proteins did in a dose-dependent manner.
authors.affiliation: Department of Biophysics, All India Institute of Medical Sciences, New Delhi. badisa55@hotmail.com
authors.forename: R B
authors.initials: RB
authors.lastname: Badisa
authors.forename: D
authors.initials: D
authors.lastname: Ganeshrao
authors.forename: R
authors.initials: R
authors.lastname: Abburi
authors.forename: T
authors.initials: T
authors.lastname: Fatma
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D002412:Cations; D002846:Chromatography, Affinity; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005296:Ferrous Compounds / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D019746:Intramolecular Oxidoreductases / Q000737:chemistry / Q000302:isolation & purification; D008545:Melanoma / Q000737:chemistry*; D008546:Melanoma, Experimental / Q000737:chemistry; D020460:Melanosomes / Q000737:chemistry*; D008562:Membrane Glycoproteins; D051379:Mice; D008969:Molecular Sequence Data; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism; D011506:Proteins / Q000737:chemistry* / Q000302:isolation & purification; D020539:Sequence Analysis, Protein; D012867:Skin / Q000737:chemistry*; D019287:Zinc Sulfate / Q000494:pharmacology; D058951:gp100 Melanoma Antigen
chemical_list: D002412:Cations; D005296:Ferrous Compounds; D008562:Membrane Glycoproteins; C548637:PMEL protein, human; C548642:Pmel protein, mouse; D011506:Proteins; D058951:gp100 Melanoma Antigen; C426865:melanosomal protein, 66-kDa, human; C426866:melanosomal protein, 66-kDa, murine; C020748:ferrous sulfate; D019287:Zinc Sulfate; D010088:Oxidoreductases; C489799:TYRP1 protein, human; C079621:Tyrp1 protein, mouse; C412191:monophenolase; C064056:tyrosinase-related protein-1; D014442:Monophenol Monooxygenase; D019746:Intramolecular Oxidoreductases; C042501:dopachrome isomerase; D002122:Calcium Chloride