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J Biol Chem. 2018 Dec 28;293(52):20157-20168. doi: 10.1074/jbc.RA118.005791. Epub 2018 Nov 1.

The melanization road more traveled by: Precursor substrate effects on melanin synthesis in cell-free and fungal cell systems.

Author information

1
From the Department of Chemistry and Biochemistry, The City College of New York and CUNY Institute for Macromolecular Assemblies, New York, New York 10031.
2
the Department of Microbiology and Immunology, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461.
3
CIC bioGUNE, Derio, Vizcaya 48160, Spain.
4
the Department of Natural Sciences, CUNY Hostos Community College, Bronx, New York 10451.
5
the City University of New York, Ph.D. Program in Biochemistry, New York, New York 10036.
6
the New York Structural Biology Center, New York, New York 10027.
7
the Department of Chemistry, CUNY Brooklyn College, Brooklyn, New York 11210.
8
the City University of New York, Ph.D. Program in Chemistry, New York, New York 10036, and.
9
the Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205.
10
From the Department of Chemistry and Biochemistry, The City College of New York and CUNY Institute for Macromolecular Assemblies, New York, New York 10031, rstark@ccny.cuny.edu.

Abstract

Natural brown-black eumelanin pigments confer structural coloration in animals and potently block ionizing radiation and antifungal drugs. These functions also make them attractive for bioinspired materials design, including coating materials for drug-delivery vehicles, strengthening agents for adhesive hydrogel materials, and free-radical scavengers for soil remediation. Nonetheless, the molecular determinants of the melanin "developmental road traveled" and the resulting architectural features have remained uncertain because of the insoluble, heterogeneous, and amorphous characteristics of these complex polymeric assemblies. Here, we used 2D solid-state NMR, EPR, and dynamic nuclear polarization spectroscopic techniques, assisted in some instances by the use of isotopically enriched precursors, to address several open questions regarding the molecular structures and associated functions of eumelanin. Our findings uncovered: 1) that the identity of the available catecholamine precursor alters the structure of melanin pigments produced either in Cryptococcus neoformans fungal cells or under cell-free conditions; 2) that the identity of the available precursor alters the scaffold organization and membrane lipid content of melanized fungal cells; 3) that the fungal cells are melanized preferentially by an l-DOPA precursor; and 4) that the macromolecular carbon- and nitrogen-based architecture of cell-free and fungal eumelanins includes indole, pyrrole, indolequinone, and open-chain building blocks that develop depending on reaction time. In conclusion, the availability of catecholamine precursors plays an important role in eumelanin development by affecting the efficacy of pigment formation, the melanin molecular structure, and its underlying scaffold in fungal systems.

KEYWORDS:

biophysics; catecholamine; cell wall; electron paramagnetic resonance (EPR); fungi; melanin; melanization; melanogenesis; nuclear magnetic resonance (NMR); pigment formation; polysaccharide; solid state NMR

PMID:
30385508
PMCID:
PMC6311522
[Available on 2019-12-28]
DOI:
10.1074/jbc.RA118.005791
[Indexed for MEDLINE]

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