Heery D M, Hoare S, Hussain S, Parker M G, Sheppard H
Department of Biochemistry, University of Leicester, University Road, Leicester LE1 7RH, United
J Biol Chem. 2001 Mar 2;276(9):6695-702. doi: 10.1074/jbc.M009404200. Epub 2000 Nov 14.
An alpha-helical motif containing the sequence LXXLL is required for the ligand-dependent binding of transcriptional co-activators to nuclear receptors. By using a peptide inhibition assay, we have defined the minimal "core" LXXLL motif as an 8-amino acid sequence spanning positions -2 to +6 relative to the primary conserved leucine residue. In yeast two-hybrid assays, core LXXLL motif sequences derived from steroid receptor co-activator (SRC1), the 140-kDa receptor interacting protein (RIP140), and CREB-binding protein (CBP) displayed differences in selectivity and affinity for nuclear receptor ligand binding domains. Although core LXXLL motifs from SRC1 and RIP140 mediated strong interactions with steroid and retinoid receptors, three LXXLL motifs present in the global co-activator CBP were found to have very weak affinity for these proteins. Core motifs with high affinity for steroid and retinoid receptors were generally found to contain a hydrophobic residue at position -1 relative to the first conserved leucine and a nonhydrophobic residue at position +2. Our results indicate that variant residues in LXXLL core motifs influence the affinity and selectivity of co-activators for nuclear receptors.
转录共激活因子与核受体的配体依赖性结合需要一个包含LXXLL序列的α-螺旋基序。通过肽抑制试验，我们将最小的“核心”LXXLL基序定义为一个8氨基酸序列，相对于主要保守亮氨酸残基跨越-2至+6位。在酵母双杂交试验中，源自类固醇受体共激活因子（SRC1）、140 kDa受体相互作用蛋白（RIP140）和CREB结合蛋白（CBP）的核心LXXLL基序序列在对核受体配体结合域的选择性和亲和力上表现出差异。尽管来自SRC1和RIP140的核心LXXLL基序介导了与类固醇和视黄酸受体的强相互作用，但发现全局共激活因子CBP中存在的三个LXXLL基序对这些蛋白的亲和力非常弱。通常发现，对类固醇和视黄酸受体具有高亲和力的核心基序在相对于第一个保守亮氨酸的-1位含有一个疏水残基，在+2位含有一个非疏水残基。我们的结果表明，LXXLL核心基序中的变异残基会影响共激活因子对核受体的亲和力和选择性。
