The second LIM domain of Lhx2 and Lhx9 family: Lhx2 and Lhx9 are highly homologous LHX regulatory proteins. They belong to the LHX protein family, which features two tandem N-terminal LIM domains and a C-terminal DNA binding homeodomain. Members of LHX family 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. Although Lhx2 and Lhx9 are highly homologous, they seems to play regulatory roles in different organs. In animals, Lhx2 plays important roles in eye, cerebral cortex, limb, the olfactory organs, and erythrocyte development. Lhx2 gene knockout mice exhibit impaired patterning of the cortical hem and the telencephalon of the developing brain, and a lack of development in olfactory structures. Lhx9 is expressed in several regions of the developing mouse brain, the spinal cord, the pancreas, in limb mesenchyme, and in the urogenital region. Lhx9 plays critical roles in gonad development. Homozygous mice lacking functional Lhx9 alleles exhibit numerous urogenital defects, such as gonadal agenesis, infertility, and undetectable levels of testosterone and estradiol coupled with high FSH levels. Lhx9 null mice are phenotypically female, even those that are genotypically male. As in other LIM domains, this domain family is 50-60 amino acids in size and shares 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.
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.",