The second LIM domain of LMO1 and LMO3 (LIM domain only protein 1 and 3)
The second LIM domain of LMO1 and LMO3 (LIM domain only protein 1 and 3): LMO1 and LMO3 are highly homologous and belong to the LMO protein family. LMO1 and LMO3 are nuclear protein that plays important roles in transcriptional regulation and development. As LIM domains lack intrinsic DNA-binding activity, nuclear LMOs are involved in transcriptional regulation by forming complexes with other transcription factors or cofactors. For example, LMO1 interacts with the the bHLH domain of bHLH transcription factor, TAL1 (T-cell acute leukemia1)/SCL (stem cell leukemia) . LMO1 inhibits the expression of TAL1/SCL target genes. LMO3 facilitates p53 binding to its response elements, which suggests that LMO3 acts as a co-repressor of p53, suppressing p53-dependent transcriptional regulation. In addition, LMO3 interacts with neuronal transcription factor, HEN2, and acts as an oncogene in neuroblastoma. Another binding partner of LMO3 is calcium- and integrin-binding protein CIB, which binds via the second LIM domain (LIM2) of LMO3. One role of the CIB/LMO3 complex is to inhibit cell proliferation. Although LMO1 and LMO3 are highly homologous proteins, they play different roles in the regulation of the pituitary glycoprotein hormone alpha-subunit (alpha GSU) gene. Alpha GSU promoter activity was markedly repressed by LMO1 but activated by LMO3. 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.",