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The third LIM domain of Four and a half LIM domains protein (FHL) The third LIM domain of Four and a half LIM domains protein (FHL): LIM-only protein family consists of five members, designated FHL1, FHL2, FHL3, FHL5 and LIMPETin. The first four members are composed of four complete LIM domains arranged in tandem and an N-terminal single zinc finger domain with a consensus sequence equivalent to the C-terminal half of a LIM domain. LIMPETin is an exception, containing six LIM domains. FHL1, 2 and 3 are predominantly expressed in muscle tissues, and FHL5 is highly expressed in male germ cells. FHL proteins exert their roles as transcription co-activators or co-repressors through a wide array of interaction partners. For example, FHL1 binds to Myosin-binding protein C, regulating myosin filament formation and sarcomere assembly. FHL2 has shown to interact with more than 50 different proteins, including receptors, structural proteins, transcription factors and cofactors, signal transducers, splicing factors, DNA replication and repair enzymes, and metabolic enzymes. FHL3 int eracts with many transcription factors, such as CREB, BKLF/KLF3, CtBP2, MyoD, and MZF_1. FHL5 is a tissue-specific coactivator of CREB/CREM family transcription factors. 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. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",