TMPred analysis predicts that isoform 2 encodes a protein identical in structure to Mcoln1, possessing 6 transmembrane domains and a channel pore, however the protein sequences diverge at amino acid 526. The 55 amino acid C-terminal cytoplasmic tail encoded by the 2.4 kb transcript is completely different from the 86 amino acid tail encoded by the murine specific 4.4 kb transcript (Fig. 4). Clontech Mouse RNA Master Blots were hybridized with the exon 2 and intron 12 probes mentioned above in an attempt to determine if these two transcripts showed differences in expression patterns, however, there was no significant difference in the 22 tissues represented (data not shown).