RESEARCH ARTICLE Molecular cloning and expression analysis of a matrix Gla protein gene in the spinyhead croaker, Collichthys lucidus.
The matrix Gla (gamma-carboxyglutamic acid-rich) protein (MGP), a vitamin K-dependent and Gla-containing protein, is a calcification inhibitor that mainly functions in tissue calcification and mineralization. In this study, we obtained the complete cDNA sequence of MGP from the spinyhead croaker (Collichthys lucidus), which we named Cl-MGP. Cl-MGP was 923 bp long with a 384-bp open reading fragment that encoded 127 amino acids. The predicted MGP protein sequence contained a 19-residue hydrophobic signal peptide, suggesting that it possesses secretory characteristics. The Gla domain and the invariant unit ErraEtCedyspC, which has been identified in all known vitamin K-dependent vertebrate proteins, were highly conserved in Cl-MGP, suggesting that it uses the same mechanism to function as the known proteins. An alignment analysis revealed that Cl-MGP had the highest identity with Larimichthys crocea (93%), which had lost five amino acid residues in the C-terminal. A quantitative real-time polymerase chain reaction revealed that Cl-MGP expression was highest in the gill, followed by the cholecyst and spleen, with almost no expression in the blood, muscle, or testes. The high Cl-MGP expression in the gill is similar to that observed in other fish species, but the relatively high expression found in the cholecyst and spleen is not seen in all species. Future studies should investigate the tissue distributions of both mRNA and proteins in different species, in order to understand the function and evolution of MGP in different species.
East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, China.
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Song
East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, China.
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Zhao
East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, China.
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Jiang
East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, China.
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Zhang
East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, China.
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Zhao
East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, China.
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Meng
East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, China swift83@sina.com.
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D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D009928:Organ Specificity / Q000235:genetics; D010473:Perciformes / Q000235:genetics*; D010802:Phylogeny; D016415:Sequence Alignment; D000097568:Matrix Gla Protein
D002135:Calcium-Binding Proteins; D018076:DNA, Complementary; D016326:Extracellular Matrix Proteins; D000097568:Matrix Gla Protein