关键词: 茶树；胞质型苹果酸脱氢酶；RTPCR；cDNA末端快速扩增法；序列分析；二级结构；

Abstract: The complete gene of cytosolic malate dehydrogenase (cMDH) from Camellia sinensis, called CscMDH, was obtained by RTPCR and rapid amplification of cDNA ends (GenBank accession number GQ845406). This gene was 1 235 bp in length, encoding a protein of 332 amino acids with the putative molecular weight of 355 kD. The Ecoli Rosetta (DE3) harboring pGEXMDH was induced by 05 mmol·L1 IPTG at 32℃ for 3 hours, and a 615 kD glutathione Stransferase (GST)fused MDH was obtained in soluble form. The results of NCBIBLAST revealed that CscMDH shared 88%-93% of amino acid sequence identity with other cMDH from different higher plants. According to the multiple sequence alignment based on the threedimensional structure of protein, CscMDH was predicted to be a dimer with thirteen βsheet and thirteen αhelix of each subunit. CscMDH contains typical fingerprint sequence (G12AAGQIG18) as all MDHs. The amino acid D43 in CscMDH is conserved in all NADMDHs. CscMDH also has some conserved sequence units homologous to other NADMDHs, such as NAD+ binding sites, catalytic motif and substrate binding sites. Moreover, CscMDH contains six Cys which are highly conserved in all plant NADcMDHs. Therefore, CscMDH was inferred to be NADdependent cMDH. The present study may provide the fundament for the further functional characterization of CscMDH.

Key words: Camellia sinensis