title: Heterogeneity of low molecular weight epidermal structural proteins of chick embryonic tarsometatarsal skin. Effect of hydrocortisone on its accumulation with reference to differentiation of epidermal cells.
abstract: Cornified layers of newly hatched chick shank skin were solubilized in 8 M urea by reduction followed by S-carboxymethylations. On Sephadex gel chromatography the solubilized proteins were separated into two distinct protein fractions (protein A and protein B). SDS-gel electrophoresis showed that the smaller protein fraction (protein B) contained two molecules with molecular weights of 15,000 and 17,000. Protein B was resolved into several fractions, pI 4.5-5.2, by preparative isoelectric focusing in the presence of 6 M urea and 0.1% Nonidet P-40. The fractions all contained the two molecules (Mr 15,000 and 17,000). The amino acid compositions of these fractions and 2-dimensional electrophoresis of epidermal protein by the method of O'Farrel indicated that the two proteins are each heterogeneous with respect to charge for reasons of microheterogeneity in the amino acid composition and varying extent of phosphorylation. When chick embryonic skin was cultured in a chemically defined medium, hydrocortisone, which induces the synthesis of protein A and results in keratinization of epidermis (Sugimoto, M., Tajima, K., Kojima, A. and Endo, H. (1974) Dev. Biol. 39, 295-307), did not accelerate the accumulation of protein B in epidermis; the normal pattern of protein B was not formed in epidermis of cultured skin with or without the hormone. Actinomycin D did not inhibit the synthesis of protein B, suggesting that the mRNA for this protein has a long life.
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002642:Chick Embryo; D004591:Electrophoresis, Polyacrylamide Gel; D000078404:Epidermal Cells; D004817:Epidermis / Q000032:analysis; D006854:Hydrocortisone / Q000494:pharmacology*; D007525:Isoelectric Focusing; D008970:Molecular Weight; D011506:Proteins / Q000032:analysis*
chemical_list: D011506:Proteins; D006854:Hydrocortisone