Figure 2.

Alternative splicing of the human mu opioid receptor, MOR-1. MOR-1 is extensively spliced in different ways in rat, mouse, and human, leading to multiple receptors, including isoforms with seven, six, and one transmembrane (TM) domains. The figure shows the genomic structure (not to scale) with alternative start sites and exon structure, and examples of different splice variants protein structures. Colours in the lower panels correspond to the exons from which each part of the protein is transcribed and/or translated. The numbers (e.g., human 12 aa) denote the length of the unique C terminus in splice variants from specific species in amino acids. Note that not all known splice variants are shown here [19]. For full coverage of the multiple splice variants of MOR-1 and the species differences, see multiple publications by G.W. Pasternak.

Source: Adapted from [123].