The induction of stress proteins was examined in rat myoblast cultures by two-dimensional gel electrophoresis. Data obtained by this analysis led to the following observations. (a) Arsenate, which behaves as a phosphate analogue in cellular phosphate-transfer reactions, stresses cultured rat cells and induces the synthesis of a unique set of proteins. (b) Most of the proteins synthesized after the addition of arsenate are identical to proteins synthesized in rat myoblasts in response to heat shock or arsenite stress. (c) However, both arsenic salts induce the synthesis of two unique proteins not induced by heat shock. (d) Five 25-30-kdalton stress proteins of rat cells do not contain methionine residues. (e) A majority of the proteins synthesized in stressed myogenic cells are also induced by stress in other rat cells such as hepatoma cells, pituitary tumor cells, and fibroblasts. The 25-30-kdalton stress-related proteins identified in myogenic cells, on the other hand, are induced in fibroblasts but not hepatoma or pituitary cells.

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