Molecular characterization of southern bluefin tuna myoglobin (Thunnus maccoyii)
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The primary structure of southern bluefin tuna Thunnus maccoyii Mb has been elucidated by molecular cloning techniques. The cDNA of this tuna encoding Mb contained 776 nucleotides, with an open reading frame of 444 nucleotides encoding 147 amino acids. The nucleotide sequence of the coding region was identical to those of other bluefin tunas (T. thynnus and T. orientalis), thus giving the same amino acid sequences. Based on the deduced amino acid sequence, bioinformatic analysis was performed including phylogenic tree, hydropathy plot and homology modeling. In order to investigate the autoxidation profiles, the isolation of Mb was performed from the dark muscle. The water soluble fraction was subjected to ammonium sulfate fractionation (60–90 % saturation) followed by preparative gel electrophoresis. Autoxidation profiles of Mb were delineated at pH 5.6, 6.5 and 7.4 at temperature 37 °C. The autoxidation rate of tuna Mb was slightly higher than that of horse Mb at all pH examined. These results revealed that tuna myoglobin was unstable than that of horse Mb mainly at acidic pH.
KeywordsMyoglobin Southern bluefin tuna cDNA cloning Autoxidation profiles
This work was partly supported by Japan Society for Promotion of Sciences (KAKENHI # 22380015 to Y. O.). The authors would like to thank Prof. Shugo Watabe, Prof. Hideki Ushio and Dr. Hideo Ozawa for their valuable suggestions throughout this study.