The PET domain of protein LIMPETin and LIM-9: Members of this family contain an N-terminal PETdomain and five to six LIM domains at the C-terminus. Four of the six LIM domains are highly homologous to the four-and-half LIM (FHL) domain family while the other two show sequence similarity to LIM domains of the Testin family. Thus, proteins of this family may be the recombinant product of genes coding testin and FHL proteins. In Schistosoma mansoni, where LIMPETin was first identified, LIMPETin is down regulated in sexually mature adult Schistosoma females compared to sexually immature adult females and adult male. Thus, proteins of this family may be the recombinant product of genes coding Testin and FHL proteins. SmLIMPETin is down regulated in sexually mature adult Schistosoma females compared to sexually immature adult females and adult males. Its differential expression indicates that it is a transcription regulator. In C. elegans, LIM-9 binds to UNC-97 and UNC-96, components of sarcomeric muscle M-lines. LIM-9 also forms a complex with SCPL-1 and UNC-89, whose function is to organize sarcomeric A-bands, especially the M-line of muscle. Thus, it might play a role in regulating the assembly and maintenance of muscle A-band. The PET domain is a protein-protein interaction domain and is usually found in conjunction with LIM domain, which is also involved in protein-protein interactions. The PET containing proteins serve as adaptors or scaffolds to support the assembly of multimeric protein complexes.
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