Figure 4.

Structural isoforms of alternatively spliced human proteins. (A) Structural alignment of the major and minor isoform in the PDZ2 domain of the protein tyrosine phosphatase PTN13_HUMAN. The two splice variants have a different affinity to the tumor suppressor protein APC (35). Isoform 4 has a 5-residue-long insertion (colored bright red) compared to the main isoform. This was the longest insertion in a splice variant in PDB where both variants are ordered at the alternative splice site. (B) The structural alignment of the two isoforms of the hexokinase KHK_HUMAN (PDB codes: 2hqqA, 3b3lA). The minor isoform contains a 44-residue substitution, which represents a paralogous local exon duplication (indicated with solid blue and red colors in 2 hqqA and 3b3lA, respectively). AS of the KHK gene selects either one or the other of two adjacent, homologous 135-bp exons.