Evidence for a Signal Sequence at the N Terminus of the Common Precursor to Adrenocorticothrophin and beta-Lipotropin in Mouse Pituitary Cells

Publisher Website
Google Scholar
Abstract
The precursor to ACTH and .beta.-endorphin was synthesized in a reticulocyte cell-free system under the direction of mRNA from mouse AtT-20 pituitary tumor cells in the presence of [3H]P, [3H]Phe, [3H]Leu, [3H]Val, [3H]Ile or [35S]Met. Automatic Edman degradation of the radioactive cell-free product showed the following N-terminal sequence: Pro-1, Met-2, Leu-11, Leu-12, Leu-13, Leu-15, Leu-16, Leu-17, Ile-21 and Val-23. The ACTH-endorphin precursor was also labeled in AtT-20 cells with [3H]Val, [3H]Leu, [3H]Trp, [3H]Ser, [35S]Met or [35S]Cys. Automatic Edman degradation of the radioactive intact cell form gave the following N-terminal sequence: Trp-1, Cys-2, Leu-3, Ser-5, Ser-6, Val-7, Cys-8, Leu-11, Leu-17, Leu-18 and tentatively Met-27. The sequence of the intact cell form from AtT-20 cells matches the sequence of the cell-free form of bovine pituitary precursor beginning at Trp-27, as determined by recombinant DNA technology. The sequence of the mouse pituitary mRNA-directed cell-free translation product also matches the bovine precursor beginning at Pro-2. Apparently both the mouse and bovine precursors possess a signal sequence of 26 amino acids which is cleaved in intact cells. CNBr cleavage of [35S]cysteine-labeled intact cell precursor gave rise to an N-terminal fragment of a size compatible with the presence of a methionyl residue at or near position 27.

This publication has 25 references indexed in Scilit: