NORMAL GENOMIC

• Zhang H et al.
• A novel C1q-domain-containing protein from Zhikong scallop Chlamys farreriwith lipopolysaccharide binding activity.
• Fish Shellfish Immunol. 2008; 25: 281-9
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• The C1q-domain-containing (C1qDC) proteins are a family of proteinscharacterized by a globular C1q (gC1q) domain in their C-terminus. Theyare involved in various processes of vertebrates and supposed to be animportant pattern recognition receptor in innate immunity ofinvertebrates. In this study, a novel member of C1q-domain-containingprotein family was identified from Zhikong scallop Chlamys farreri(designated as CfC1qDC) by expressed sequence tag (EST) and rapidamplification of cDNA ends (RACE) approaches. The full-length cDNA ofCfC1qDC was of 777 bp, consisting of a 5'-terminal untranslated region(UTR) of 62 bp and a 3' UTR of 178 bp with a polyadenylation signalsequence AATAAA and a poly (A) tail. The CfC1qDC cDNA encoded apolypeptide of 178 amino acids, including a signal peptide and aC1q-domain of 158 amino acids with the theoretical isoelectric point of5.19 and the predicted molecular weight of 17.2 kDa. The C1q-domain inCfC1qDC exhibited homology with those in sialic acid binding lectin frommollusks and C1qDC proteins from higher vertebrates. The typical 10beta-strand jelly-roll folding topology structure of C1q-domain and theresidues essential for effective packing of the hydrophobic core were wellconserved in CfC1qDC. By fluorescent quantitative real-time PCR, mRNAtranscripts of CfC1qDC were mainly detected in kidney, mantle, adductormuscle and gill, and also marginally detectable in hemocytes. In thebacterial challenge experiment, after the scallops were challenged byListonella anguillarum, there was a significant up-regulation in therelative expression level of CfC1qDC and at 6h post-injection, the mRNAexpression reached the maximum level and was 4.55-fold higher than that ofcontrol scallops. Similarly, the expression of CfC1qDC mRNA in mixedprimary cultures of hemocytes stimulated by lipopolysaccharides (LPS) wasup-regulated and reached the maximum level at 6h post-stimulation, andthen dropped back to the original level gradually. In order to investigateits function, the cDNA fragment encoding the mature peptide of CfC1qDC wasrecombined and expressed in Escherichia coli BL21(DE3). The recombinantCfC1qDC protein displayed a significantly strong activity to bind LPS fromE. coli, although no obvious antibacterial or agglutinating activitytoward Gram-negative bacteria E. coli JM109, L. anguillarum andGram-positive bacteria Micrococcus luteus was observed. These resultssuggested that CfC1qDC was absolutely a novel member of the C1qDC proteinfamily and was involved in the recognition of invading microorganismsprobably as a pattern recognition molecule in mollusk.

• Konrat R, Weiskirchen R, Krautler B, Bister K
• Solution structure of the carboxyl-terminal LIM domain from quailcysteine-rich protein CRP2.
• J Biol Chem. 1997; 272: 12001-7
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• Proteins of the cysteine-rich protein (CRP) family (CRP1, CRP2, and CRP3)are implicated in diverse processes linked to cellular differentiation andgrowth control. CRP proteins contain two LIM domains, each formed by twozinc-binding modules of the CCHC and CCCC type, respectively. The solutionstructure of the carboxyl-terminal LIM domain (LIM2) from recombinantquail CRP2 was determined by multidimensional homo- and heteronuclearmagnetic resonance spectroscopy. The folding topology retains bothindependent zinc binding modules (CCHC and CCCC). Each module consists oftwo orthogonally arranged antiparallel beta-sheets, and thecarboxyl-terminal CCCC module is terminated by an alpha-helix. 15Nmagnetic relaxation data indicate that the modules differ in terms ofconformational flexibility. They pack together via a hydrophobic coreregion. In addition, Arg122 in the CCHC module and Glu155 in the CCCCmodule are linked by an intermodular hydrogen bond and/or salt bridge.These residues are absolutely conserved in the CRP family of LIM proteins,and their interaction might contribute to the relative orientation of thetwo zinc-binding modules in CRP LIM2 domains. The global fold of quailCRP2 LIM2 is very similar to that of the carboxyl-terminal LIM domain ofthe related but functionally distinct CRP family member CRP1, analyzedrecently. The carboxyl-terminal CCCC module is structurally related to theDNA-binding domain of the erythroid transcription factor GATA-1. In thetwo zinc-binding modules of quail CRP2 LIM2, flexible loop regions made upof conserved amino acid residues are located on the same side of the LIM2domain and may cooperate in macromolecular recognition.