Analysis of the fatty acid components in a perchloric acid-soluble protein

We had previously found that a perchloric acid-soluble protein (PSP1) occur s in rat liver, and that this novel protein inhibits protein synthesis in a rabbit reticulocyte lysate system (T. Oka, H. Tsuji, C. Noda, K. Sakai, Y. -H. Hong, I. Suzuki, S. Munoz, Y. Natori, J. Biol. Chem. 270 (1995) 30060-3 0067). In the present study, we analyzed lipid components bound to PSP1. Na tive PSP1 was purified from rat liver using Sephadex G-75, DE,52 cellulose and IgGPSP-affinity chromatography, and the lipid components were extracted . The components obtained from the purified PSP1 were shown to be free fatt y acids by thin-layer chromatography. By GC-MS, six major fatty acids were identified as 14:0, 16:0, 18:0, 18:1, 18:2 and 20:4. 1 mel of PSP1 containe d 1.26 mel of total fatty acid components. The fatty acid-binding assay of PSP1 showed that the B-max was 1.25 mel fatty acid/mol PSP1 and the K-d val ue for palmitic acid was 6.03 mu M. The concentration of PSP1 mRNA in rat l iver increased 2.3-fold by the administration of peroxisome proliferator, b ezafibrate. These findings show that PSP1 is a fatty acid-binding protein-l ike protein, which is involved in the intracellular metabolism of fatty aci d and is quite different from the known fatty acid-binding proteins. (C) 19 99 Elsevier Science B.V. All rights reserved.