Melanosome--a sophisticated organelle

Melanosome is a clear out organelle of its own. The experience of the authors in the melanosome investigation has been reviewed and put to context with the literature data. Melanin moiety, a prominent feature of melanosome, was found to vary between 20-60 weight %. Melanosome concentration in pigment tissues was demonstrated to be remarkably high which explains their capacity to perform various functions both cytoprotective and cytotoxic-ascribed to the presence of melanin. Putative relation of melanosomes to other cell organelles was critically analysed. Systems of melanosome maturation were explained. The ultrastructure of melanosomes determined by the quality of their protein matrix was described and basic morphometric data summarized. The importance of the compartmentalization of melanogenesis was underlined and the fragility of melanosomal limiting membrane shown. The melanosome degradation repeatedly observed by electron microscopy has not been confirmed by biochemical means.