The second LIM domain of Lmx1a and Lmx1b: Lmx1a and Lmx1b 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. Mouse Lmx1a is expressed in multiple tissues, including the roof plate of the neural tube, the developing brain, the otic vesicles, the notochord, and the pancreas. In mouse, mutations in Lmx1a result in failure of the roof plate to develop. Lmx1a may act upstream of other roof plate markers such as MafB, Gdf7, Bmp6, and Bmp7. Further characterization of these mice reveals numerous defects including disorganized cerebellum, hippocampus, and cortex; altered pigmentation; female sterility, skeletal defects, and behavioral abnormalities. In the mouse, Lmx1b functions in the developing limbs and eyes, the kidneys, the brain, and in cranial mesenchyme. The disruption of Lmx1b gene results kidney and limb defects. In the brain, Lmx1b is important for generation of mesencephalic dopamine neurons and the differentiation of serotonergic neurons. In the mouse eye, Lmx1b regulates anterior segment (cornea, iris, ciliary body, trabecular meshwork, and lens) development. 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.",