The second LIM domain of Isl, a member of LHX protein family
The second LIM domain of Isl: Isl is a member of LHX protein family, which features two tandem N-terminal LIM domains and a C-terminal DNA binding homeodomain. Isl1 and Isl2 are the two conserved members of this family. Proteins in this group are found in the nucleus and act as transcription factors or cofactors. LHX proteins are critical for the development of specialized cells in multiple tissue types, including the nervous system, skeletal muscle, the heart, the kidneys, and endocrine organs, such as the pituitary gland and the pancreas. Isl-1 is one of the LHX proteins isolated originally by virtue of its ability to bind DNA sequences from the 5'-flanking region of the rat insulin gene in pancreatic insulin-producing cells. Mice deficient in Isl-1 fail to form the dorsal exocrine pancreas and islet cells fail to differentiate. On the other hand, Isl-1 takes part in the pituitary development by activating the gonadotropin-releasing hormone receptor gene together with LHX3 and steroidogenic factor 1. Mouse Isl2 is expressed in the retinal ganglion cells and the developing spinal cord where it plays a role in motor neuron development. Same as Isl1, Isl2 may also be able to bind to the insulin gene enhancer to promote gene activation. All 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.",