| This revealed that the binding of 15 . 5K to the box C / D motif is essential for the association of the remaining snoRNP associated proteins , namely , NOP 56 , NOP 58 , fibrillarin , and the nucleoplasmic proteins TIP 48 and TIP 49 . ^^^ Stem 2 of the box C / D motif , in contrast to the U 4 5 ' stem loop , is highly conserved , and we show that this sequence is responsible for the binding of NOP 56 , NOP 58 , fibrillarin , TIP 48 , and TIP 49 , but not of 15 . 5K , to the snoRNA . ^^^ |