PM2, a group 3 LEA protein from soybean, and its 22-mer repeating region confer salt tolerance in Escherichia coli.
To have knowledge of the effect of soybean PM2 protein in protecting dehydrated cells and its functional region, PM2 cDNA was isolated from soybean immature seeds. The recombinants expressing full-length PM2, truncated polypeptides of PM2A (aa 1-262) or PM2B (aa 129-262, 22-mer repeating region), or artificial polypeptide PM2C (duplication of 22-mer repeating region) were constructed. By using SDS-PAGE and mass spectrometry approaches, these fusion polypeptides were identified and proved to be hydrophilic and heat-stable. Spot assays of BL/PM2 and BL/pET28 (as control) showed that protein PM2 increased salt tolerance (500 mM NaCl or 500 mM KCl) of Escherichia coli, rather than osmotic tolerance (1100 mM sorbitol). In addition, comparing the survival ratios of the transformants under 500 mM NaCl or 500 mM KCl stresses, the results showed that: (1) the survival ratios of BL/PM2 and BL/PM2B were quite similar, both showing much higher values than those of BL/pET28. (2) The survival ratios of BL/PM2C were much higher than those of BL/PM2, BL/PM2A, and BL/PM2B. This provides the first experimental evidence that PM2 polypeptide enhances salt tolerance of E. coli cells, and the 22-mer repeat region is an important functional region.
Liu
Yun
Y
Institute of Genetics and Cytology, School of Life Science, Northeast Normal University, Changchun 130024, PR China.
Zheng
Yizhi
Y
D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics*; D006358:Hot Temperature; D013058:Mass Spectrometry; D010455:Peptides / Q000032:analysis / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D011994:Recombinant Proteins / Q000032:analysis / Q000737:chemistry; D020449:Repetitive Sequences, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology; D012995:Solubility; D030262:Soybean Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D014169:Transformation, Bacterial
D010455:Peptides; D010940:Plant Proteins; D011994:Recombinant Proteins; D030262:Soybean Proteins; C066246:late embryogenesis abundant protein, plant; D012965:Sodium Chloride; D011189:Potassium Chloride