Calreticulin (CRT) is a highly conserved Ca²⁺-binding protein and chaperone in the endoplasmic reticulum, which mainly participates in adjusting calcium level and directing proper conformation of proteins. Here, we cloned the crt gene of the scleractinian coral Galaxea astreata, named Gacrt, and analysed its ability to drive bacterial agglutination. The full-length Gacrt cDNA consisted of 1 792 nucleotides and contained a 77 bp 5′ untranslated region (UTR), a 380 bp 3′ UTR and a 1 335 bp open reading frame (ORF) that encoded a 444 amino acid protein. The deduced peptide possessed a signal peptide domain, an endoplasmic reticulum retrieval signal sequence (KDEL), two potential calreticulin family signature motifs and a set of triplicate repeats. We also found that the recombinant GaCRT protein could promote agglutination of both the Gram-positive bacterium Micrococcus luteus and the Gram-negative bacterium Escherichia coli. These results show that the GaCRT protein can enhance bacterial agglutination, hinting that GaCRT is an immune-relevant molecule involved in host defense against bacterium.

中文翻译：

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巩膜珊瑚Galaxea astreata中钙网蛋白基因的克隆和功能分析

钙网蛋白（CRT）是内质网中一种高度保守的Ca ²⁺结合蛋白和伴侣蛋白，其主要参与调节钙水平和指导蛋白质的正确构象。在这里，我们克隆了巩膜珊瑚Galaxea astreata的crt基因，称为Gacrt，并分析了其驱动细菌凝集的能力。全长盖特cDNA由1 792个核苷酸组成，包含一个77 bp的5'非翻译区（UTR），一个380 bp的3'UTR和一个1 335 bp的开放阅读框（ORF），其编码444个氨基酸。推导的肽具有信号肽结构域，内质网检索信号序列（KDEL），两个潜在的钙网蛋白家族签名基序和一组三重复。我们还发现，重组GaCRT蛋白可以促进革兰氏阳性细菌微球菌和革兰氏阴性细菌大肠杆菌的凝集。这些结果表明，GaCRT蛋白可以增强细菌凝集作用，表明GaCRT是与宿主防御细菌有关的免疫相关分子。