Fig. 1. The npc2 gene family in Drosophila melanogaster. (A) The gene structure and the phylogenetic tree of eight npc2-like genes. Two gene clusters contain five npc2-like genes (CG31410, CG12813 and CG3934; CG11314 and CG11315), which can be identified based upon protein sequence similarities and gene location. (B) Protein sequence alignment of Npc2 proteins. hNpc2, homo sapiens NPC2; CeNpc2, Caenorhabdtis elegans Npc2 (NCR-2); ScNpc2p, Saccharomyces cerevisiae Npc2. 1, 2, 3 indicate the positions of three intron positions described in the text. 4 marks the intron position of C. elegans npc2 (ncr-2). The asterisks denote the five key residues previously found to be important for Npc2 function.