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Mol Biol Rep (2013) 40:12551263 DOI 10.1007/s11033-012-2168-9
Molecular cloning and characterization of S-adenosylmethionine synthetase gene from Lycoris radiata
Xiao-Dan Li Bing Xia Ren Wang
Sheng Xu Yu-Mei Jiang Fang-Bo Yu
Feng Peng
Received: 2 February 2012 / Accepted: 8 October 2012 / Published online: 18 October 2012 Springer Science+Business Media Dordrecht 2012
Abstract S-adenosylmethionine (SAM) synthetase catalyzes the synthesis of SAM, a molecule important for all cellular organisms. It is also considered to play an important role in salt tolerance of plants. Here, we cloned a Lycoris radiata (L. radiata) SAM synthetase gene LrSAMS to determine its biological function. The gene encodes a protein of 401 amino acids with a calculated molecular weight of 43.9 kDa. Amino acid sequence analysis of the deduced protein LrSAMS reveals high sequence identity to SAM synthetases from other organisms, such as Arabidopsis thaliana and Oryza sativa. The deduced LrSAMS protein contains conserved amino acids residues and sequences motifs that closely related to the function of SAM synthetase. Otherwise, the transcript levels of LrSAMS were signicantly induced by NaCl treatment inL. radiata leaves, which implied that LrSAMS might play an important role in tolerance to salt stress in L.radiata. Complete ORF of LrSAMS was inserted into expression vector pET-29a(?) and transformed into Escherichia coli BL21 (DE3). The difference between the growth curve of the transgenic strain and control strain with blank vector showed that over-expressing LrSAMS could provide
growth advantage to the engineered strain in high salt concentration.
Keywords S-adenosylmethionine synthetase
Lycoris radiata Salt stress
Introduction
S-adenosylmethionine (SAM or AdoMet) is an essential intermediate in the physiology of all organisms [1], it is a biologically active molecule involved in a number of biochemical reactions. SAM is the main methyl donor and plays a central role in most methylation reactions, such as the methylation of nucleic acids, proteins, lipids, and polysaccharides [2]. It also acts as a precursor of polyamines (PAs), as well as a precursor to the 50-deoxyadenosyl radical used by some enzymes [35].
S-adenosylmethionine synthetase (SAM synthetase; EC2.5.1.6) is a housekeeping enzyme that catalyzes the only known route of SAM biosynthesis using methionine (Met) and ATP as substrates. It was rstly described by Cantoni [6], it has been demonstrated that almost all organisms have a functional SAM synthetase and...