Abstract
Melanosome biogenesis and function were studied after purification of early stage melanosomes and characterization of specific proteins sorted to that organelle. Melanosomes were isolated from highly pigmented human MNT1 melanoma cells after disruption and initial separation by sucrose density gradient centrifugation. Low-density sucrose fractions were found by electron microscopy to be enriched in stage I and stage II melanosomes, and these fractions were further separated and purified by free flow electrophoresis. Tyrosinase and dopachrome tautomerase (DCT) activities were found exclusively in stage II melanosomes, even though DCT (and to some extent tyrosinase) proteins were sorted to stage I melanosomes. Western immunoblotting revealed that these catalytic proteins, as well as TYRP1, MART1, and GP100, were cleaved and inactivated in stage I melanosomes. Proteolytic cleavage was critical for the refolding of GP100 within the melanosomal milieu, and subsequent reorganization of amorphous stage I melanosomes into fibrillar, ovoid, and highly organized stage II melanosomes appears to stabilize the catalytic functions of melanosomal enzymes and allows melanin biosynthesis to begin. These results provide a better understanding of the structural features seen during melanosome biogenesis, and they yield further clues as to the physiological regulation of pigmentation.
Bibliography
Kushimoto, T., Basrur, V., Valencia, J., Matsunaga, J., Vieira, W. D., Ferrans, V. J., Muller, J., Appella, E., & Hearing, V. J. (2001). A model for melanosome biogenesis based on the purification and analysis of early melanosomes. Proceedings of the National Academy of Sciences, 98(19), 10698â10703.
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Dates
Type | When |
---|---|
Created | 23 years, 1 month ago (July 26, 2002, 10:44 a.m.) |
Deposited | 3 years, 4 months ago (April 13, 2022, 5:36 a.m.) |
Indexed | 3 weeks, 4 days ago (Aug. 3, 2025, 6:48 p.m.) |
Issued | 24 years ago (Aug. 28, 2001) |
Published | 24 years ago (Aug. 28, 2001) |
Published Online | 24 years ago (Aug. 28, 2001) |
Published Print | 23 years, 11 months ago (Sept. 11, 2001) |
@article{Kushimoto_2001, title={A model for melanosome biogenesis based on the purification and analysis of early melanosomes}, volume={98}, ISSN={1091-6490}, url={http://dx.doi.org/10.1073/pnas.191184798}, DOI={10.1073/pnas.191184798}, number={19}, journal={Proceedings of the National Academy of Sciences}, publisher={Proceedings of the National Academy of Sciences}, author={Kushimoto, Tsuneto and Basrur, Venkatesha and Valencia, Julio and Matsunaga, Jun and Vieira, Wilfred D. and Ferrans, Victor J. and Muller, Jacqueline and Appella, Ettore and Hearing, Vincent J.}, year={2001}, month=aug, pages={10698–10703} }