The third LIM domain of Enigma-like family: The Enigma LIM domain family is comprised of three members: Enigma, ENH, and Cypher (mouse)/ZASP (human). These subfamily members contain a single PDZ domain at the N-terminus and three LIM domains at the C-terminus. Enigma was initially characterized in humans and is expressed in multiple tissues, such as skeletal muscle, heart, bone, and brain. The third LIM domain specifically interacts with the insulin receptor and the second LIM domain interacts with the receptor tyrosine kinase Ret and the adaptor protein APS. Thus Enigma is implicated in signal transduction processes, such as mitogenic activity, insulin related actin organization, and glucose metabolism. The second member, ENH protein, was first identified in rat brain. It has been shown that ENH interacts with protein kinase D1 (PKD1) via its LIM domains and forms a complex with PKD1 and the alpha1C subunit of cardiac L-type voltage-gated calcium channel in rat neonatal cardiomyocytes. The N-terminal PDZ domain interacts with alpha-actinin at the Z-line. ZASP/Cypher is required for maintenance of Z-line structure during muscle contraction, but not required for Z-line assembly. In heart, Cypher/ZASP plays a structural role through its interaction with cytoskeletal Z-line proteins. In addition, there is increasing evidence that Cypher/ZASP also performs signaling functions. Studies reveal that Cypher/ZASP interacts with and directs PKC to the Z-line, where PKC phosphorylates downstream signaling targets. LIM domains are 50-60 amino acids in size and share two characteristic zinc finger motifs. The two zinc fingers contain eight conserved residues, mostly cysteines and histidines, which coordinately bond to two zinc atoms. LIM domains function as adaptors or scaffolds to support the assembly of multimeric protein complexes.
Comment:The two zinc fingers contain eight conserved residues, mostly cysteines and histidines, which coordinately bond to two zinc atoms. The Zn binding residues of LIM domain are highly conserved.
Jiyao W et al.(2023). "The conserved domain database in 2023.",