Xuemei Sun

Publications (2)7.11 Total impact

• Article: Identification, expression and antibacterial activity of a tachylectin-related homolog in amphioxus Branchiostoma belcheri with implications for involvement of the digestive system in acute phase response.

  Lingyan Ju, Shicui Zhang, Yujun Liang, Xuemei Sun
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  ABSTRACT: Tachylectin-related proteins have been identified in various organisms from slime molds to sponges to bony fish, yet little is known to date about it in protochordate amphioxus, an important organism occupying a nodal position from invertebrates to vertebrates. Moreover, if the protein acts as an immune-relevant molecule remains controversial. Here we demonstrated the presence of a tachylectin-related gene in Branchiostoma belcheri. The predicted gene product, termed BbTL, consists of 305 amino acids with a putative N-terminal signal peptide and 6 tachylectin-typical tandem repeats of 30-33 amino acids. In situ hybridization histochemistry indicates a tissue-specific expression pattern of BbTL in adult amphioxus with the most abundant expression in the hepatic caecum and hind-gut. Quantitative real-time PCR reveals that challenge with LPS results in a significant up-regulation of BbTL expression in the guts. In addition, the recombinant BbTL expressed in Pichia pastoris is able to inhibit the growth of Gram-negative bacterium Escherichia coli in a dose-dependent manner. All these suggest that BbTL, like most other tachylectin-related proteins, is involved in the host immune defense, and the digestive system of B. belcheri appears the major immune tissue responding to LPS challenge.
  Fish &amp Shellfish Immunology 12/2008; 26(2):235-42. · 3.32 Impact Factor
• Article: The ycaC-related protein from the amphioxus Branchiostoma belcheri (BbycaCR) interacts with creatine kinase.

  Shengjuan Jiang, Xuemei Sun, Shicui Zhang
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  ABSTRACT: The ycaC-related gene, ycaCR, is uncharacterized, and has no assigned function to date. Here we clearly showed that the ycaC-related gene from the amphioxus Branchiostoma belcheri, BbycaCR, coded for a novel member of the isochorismatase superfamily, which is mainly localized in the mitochondrial fraction. Both pull-down and reverse pull-down analyses revealed that BbycaCR was able to interact with creatine kinase, an enzyme involved in energy transduction, in addition to binding to native ycaCR, forming a homopolymer. Surprisingly, neither isochorismatase, nicotinamidase nor N-carbamoylsarcosine amidohydrolase activity was detected for BbycaCR, although it possessed the putative catalytic triad of Asp19, Arg(Lys)84 and Cys118 that is found in ycaC proteins. Both tissue section in situ hybridization and immunohistochemistry showed that BbycaCR was ubiquitously expressed in amphioxus, although at different expression levels, suggesting that BbycaCR plays a conserved fundamental cellular role in amphioxus. It is proposed that BbycaCR may be indirectly involved in energy transduction.
  FEBS Journal 09/2008; 275(18):4597-605. · 3.79 Impact Factor