Freeze-fracture study of melanosomes in mammalian epidermis and the distribution of intramembrane particles in the melanosome membrane.
The ultrastruct of melanosomes in mammalian epidermis has been studied using the freeze-fracture technique. The internal structure of the melanosome, as seen in cross-fractured granules, consists of a very fine particulate matter. There is no evidence of an internal membranous structure in melanosomes, indicating that the internal matrix which is characteristic of ultra-thin sectioned material most likely represents cross-linked protein fibers. Fracture "en-face' of the melaosome limiting membrane reveals a random distribution of intramembrane particles on both the P- and E-faces of the membrane. There is a significantly higher density of IMPs on the P-face. The IMPs of the melanosome membrane may be involved in (a) selective passage of ions through the membrane, (b) membrane transducing events, and/or (c) anchoring sites for cytoplasmic fibrils and microfilaments.
D000818:Animals; D002462:Cell Membrane / Q000648:ultrastructure; D005614:Freeze Fracturing; D006168:Guinea Pigs; D007291:Inosine Monophosphate / Q000032:analysis; D008544:Melanocytes / Q000648:ultrastructure*; D008565:Membrane Proteins / Q000032:analysis; D012867:Skin / Q000166:cytology*
D008565:Membrane Proteins; D007291:Inosine Monophosphate