1F9B

MELANIN PROTEIN INTERACTION: X-RAY STRUCTURE OF THE COMPLEX OF MARE LACTOFERRIN WITH MELANIN MONOMERS

Summary for 1F9B

• Entry DOI: 10.2210/pdb1f9b/pdb
• Related: 1B1X
• Descriptor: LACTOTRANSFERRIN, FE (III) ION, BICARBONATE ION, ... (5 entities in total)
• Functional Keywords: lactoferrin, idq molecule, complex, melanin, iron transport, metal-binding, metal transport
• Biological source: Equus caballus (horse)
• Cellular location: Secreted: O77811
• Total number of polymer chains: 1
• Total formula weight: 76618.17

Authors

Kumar, S.,Singh, T.P.,Sharma, A.K.,Singh, N.,Raman, G. (deposition date: 2000-07-10, release date: 2001-02-10, Last modification date: 2024-10-30)

Primary citation

Sharma, A.K.,Kumar, S.,Sharma, V.,Nagpal, A.,Singh, N.,Tamboli, I.,Mani, I.,Raman, G.,Singh, T.P.
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.
Proteins, 45:229-236, 2001

PubMed Abstract: The 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.

PubMed: 11599026
DOI: 10.1002/prot.1143

Experimental method

X-RAY DIFFRACTION (2.7 Å)