Interaction of human substantia nigra neuromelanin with lipids and peptides.
Neuromelanin was isolated from human substantia nigra using different procedures. In the pigment isolated by any of these procedures a peptide component covalently bound to the melanic structure was found, as shown by treatment with reagents known to eliminate noncovalently bound proteins. The amino acid content of such a peptide component was reproducible and corresponded to approximately 15% of the neuromelanin weight. Neuromelanin also showed the ability to absorb specifically lipid molecules, approximately 20% of its weight, and among these lipids cholesterol was identified, constituting approximately 5% of the total lipid mixture. A synthetic melanin, incubated with putamen homogenate, bound tissue peptides with an amino acid content quite close to that of neuromelanin. The same synthetic melanin adsorbed a lower amount of lipids from the putamen homogenate compared with neuromelanin. The sulfur content of neuromelanin was also reproducible even using different isolation procedures. A nonpigmented tissue like corpus callosum was used as a control and extracted by the method used for neuromelanin isolation; a total elimination of tissue components was found, thus demonstrating the capability of the reported procedures to isolate neuromelanin alone. The presence of a peptide component in the neuromelanin structure and the selective affinity for lipid molecules suggest new aspects of the functional role and metabolic pathway of neuromelanin.
Zecca
L
L
Institute of Advanced Biomedical Technologies-CNR, University of Milan, Italy. zecca@itba.mi.cnr.it
Costi
P
P
Mecacci
C
C
Ito
S
S
Terreni
M
M
Sonnino
S
S
D000368:Aged; D000369:Aged, 80 and over; D000596:Amino Acids / Q000378:metabolism; D003337:Corpus Callosum / Q000737:chemistry / Q000378:metabolism; D019286:Endopeptidase K; D006801:Humans; D050356:Lipid Metabolism; D009682:Magnetic Resonance Spectroscopy; D008543:Melanins / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D008875:Middle Aged; D009479:Neuropeptides / Q000378:metabolism*; D010300:Parkinson Disease / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000502:physiology; D011522:Protons; D013378:Substantia Nigra / Q000737:chemistry / Q000378:metabolism*; D013455:Sulfur / Q000032:analysis
D000596:Amino Acids; D008543:Melanins; D009479:Neuropeptides; D011522:Protons; C014121:neuromelanin; D013455:Sulfur; D019286:Endopeptidase K