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MELANIN PROTEIN INTERACTION: X-RAY STRUCTURE OF THE COMPLEX OF MARE LACTOFERRIN WITH MELANIN MONOMERS
Structural highlights
FunctionTRFL_HORSE Transferrins are iron binding transport proteins which can bind two Fe(3+) ions in association with the binding of an anion, usually bicarbonate. The lactotransferrin transferrin-like domain 1 functions as a serine protease of the peptidase S60 family that cuts arginine rich regions. This function contributes to the antimicrobial activity (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe concentration of melanin determines the intensity of colors of the skin and hair of animals. Melanin pigments are tyrosine-based polymers formed in melanocytes within specialized organelles called melanosomes. In order to understand the mechanism of melanin polymerization, lactoferrin, a basic protein with a pI value of 9.0, has been used to produce melanin. Lactoferrin is a monomeric iron-binding protein with a molecular weight of 80 kDa. The crystals of lactoferrin were soaked in a solution containing dihydroxyphenylalanine (DOPA) and tyrosinase enzyme. These crystals were used for X-ray intensity data collection. The intensity data were collected to 2.7-A resolution to an overall completeness of 91% with an R(sym) of 0.071. The crystals belong to orthorhombic space group P2(1)2(1)2(1) with cell dimensions: a = 85.0 A, b = 99.8 A, c = 103.4 A. The structure was determined by molecular replacement method, using the model of diferric mare lactoferrin, and refined to an R-factor 0.215 (R(free) = 0.287) for all the data to 2.7-A resolution. The final model comprises 5,281 protein atoms from 689 amino acids, 2Fe(3+), 2CO(2-)(3) ions, 2 indole-5,6-quinone molecules (IQ), and 73 water molecules. Two IQ molecules, one in each lobe, bind to lactoferrin. In the C-lobe, the IQ binds in the iron-binding cleft, whereas in the N-lobe, it is located in the side pocket between two alpha-helices, filled with solvent molecules in the native iron-saturated mare lactoferrin. The IQ molecules interact with protein molecule mainly through glutamic acid in both lobes, without significant perturbation to the protein structure. The orientation of N- and C-lobes in the present structure is similar to that observed in the native iron-saturated protein. However, as a result of the binding of IQ molecules, the orientations of the domains N1, N2 and C1, C2 in the two cases differ slightly. Lactoferrin-melanin interaction and its possible implications in melanin polymerization: crystal structure of the complex formed between mare lactoferrin and melanin monomers at 2.7-A resolution.,Sharma AK, Kumar S, Sharma V, Nagpal A, Singh N, Tamboli I, Mani I, Raman G, Singh TP Proteins. 2001 Nov 15;45(3):229-36. PMID:11599026[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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