text: Nuclear receptors bind to coactivators in a ligand-dependent manner.  A common feature of nuclear receptor coactivators is that they contain one or more LXXLL binding motifs (a contiguous sequence of 5 amino acids where L = leucine and X = any amino acid) referred to as NR (nuclear receptor) boxes.  The LXXLL binding motifs have been shown by X-ray crystallography to bind to a groove on the surface of ligand binding domain of nuclear receptors.  Examples include:
  * ARA (androgen receptor associated protein)
  ** ARA54 ()
  ** ARA55 ()
  ** ARA70 ()
  * AIRE
  * BCAS3 (breast carcinoma amplified sequence 3)
  * CREB-binding protein
  * CRTC (CREB regulated transcription coactivator)
  ** CRTC1 ()
  ** CRTC2 ()
  ** CRTC3 ()
  * CARM1 (coactivator-associated arginine methyltransferase 1) 
  * Nuclear receptor coactivator (NCOA)
  ** NCOA1/SRC-1 (steroid receptor coactivator-1)/ 
  ** NCOA2/GRIP1 (glucocorticoid receptor interacting protein 1)/ TIF2 (transcriptional intermediary factor 2)  
  ** NCOA3/AIB1 (amplified in breast)  
  ** NCOA4/ARA70 (androgen receptor associated protein 70)  
  ** NCOA5 () 
  ** NCOA6 ()
  ** NCOA7 ()
  * p300 
  * PCAF (p300/CBP associating factor) 
  * PGC1 (proliferator activated receptor gamma coactivator 1)
  ** PPARGC1A ()
  ** PPARGC1B ()
  * PNRC (proline-rich nuclear receptor coactivator 1)
  ** PNRC1 ()
  ** PNRC2 ()