title: Characterization of alpha-MSH-induced changes in the phosphorylation of a 53 kDa protein in Xenopus melanophores.
abstract: alpha-Melanotropin has been shown to induce specific changes in the degree of phosphorylation of a 53 kDa melanophore protein, concomitant with pigment dispersion. To further characterize the alpha-MSH-induced changes in 53 kDa phosphorylation in melanophores from the ventral tail-fin of Xenopus tadpoles, we investigated the concentration and time dependency of the effect. A significant increase in 53 kDa phosphorylation was detectable at 5 X 10(-8) M alpha-MSH. The maximal increase in 53 kDa phosphorylation was found after an incubation time of 10-15 min, whereas pigment dispersion was optimal after 60 min. The phosphorylated 53 kDa band showed clear cross-reactivity with monoclonal anti-beta-tubulin, and migrates as a single protein after two-dimensional (2D) separation. On a 2D-separation system the 53 kDa protein (IEP 5.1) migrated in the acidic tail of purified beta-tubulin. Our data strongly indicate that the 53 kDa protein is a beta-tubulin-like protein. We suggest that the degree of 53 kDa phosphorylation may be an important factor in the regulation of microtubule function in melanophores.
mesh_terms: D000818:Animals; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007526:Isoelectric Point; D007814:Larva; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D008547:Melanophores / Q000187:drug effects*; D008870:Microtubules / Q000502:physiology; D008970:Molecular Weight; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D014404:Tubulin / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: D010750:Phosphoproteins; D014404:Tubulin; D009074:Melanocyte-Stimulating Hormones