Goose fatty acid synthetase mRNA.

The fatty acid synthetase of animal tissues consists of two identical subunits (Mr = 250,000), each of which is a multienzyme protein containing domains for the acyl carrier peptide and the seven different catalytic activities required for the conversion of acetyl-CoA and malonyl-CoA to palmitate. Total poly(A+) RNA was isolated from goose uropygial gland and translated in a cell-free rabbit reticulocyte system. The translation products contained a polypeptide having the same molecular weight as the native synthetase subunits; this protein was specifically recognized by anti-synthetase antibodies and could be competed by excess native synthetase for antibody binding. Fractionation of the poly(A+) RNA by sucrose gradient centrifugation showed that synthetase mRNA is very large, repeatedly exhibiting a sedimentation coefficient of 35 S. Gel electrophoresis of this purified mRNA fraction following glyoxylation showed the presence of several species of RNA, one of which correlated well with the in vitro translation of the synthetase. This mRNA species has a molecular weight of 2.95 X 10(6), which is large enough to code for a protein with a molecular weight of 250,000. These results confirm the multifunctional nature of the synthetase and indicate that the synthetase subunit must arise as a single polypeptide chain synthesized from one contiguous mRNA.