Abstract
Previous studies revealed that a group of Hsc70 proteins disappeared gradually, which another group of Hsc70 emerged in mung bean seedling during germination. The purpose of this study is to examine the expression of Hsc70 during seed germination and embryogenesis. The Hsc70 proteins in seeds and seedling at 1 day after germination were analyzed by mass spectrometer. Dry seeds of mung bean contain two different Hsc70s, while seedlings of 1 dag contain only one Hsc70. The Hsc70 in seedling is different from the Hsc70s in seeds. The Hsc70 in seedling at 1 day after germination has higher molecular weight and hydrophobicity than Hsc70s in seeds. The Hsc70s present abundantly in flower bud, flower and younger legumes. During embryogenesis, the Hsc70 accumulate gradually in seeds, while decrease gradually in pods.The substrate-binding domain of Hsc70s from bacteria, yeast and vertebrates are effective in forming complexes with FYQLALT. In contrast, the substrate-binding domain of Hsc70s from Arobidopsis and mung bean are ineffective for forming complexes with FYQLALT. Heptapetides were selected by affinity panning of phage peptide display libraries using purified the Hsc70 at 1 day after germination. After three rounds of heptapeptides selection, we obtained five different heptapeptide sequences. In these heptapeptides, the first residue is always hydrophobic, and the fifth residue has a high frequency to be positively charged. Among five selected heptapeptides, PTHRHRT exhibited the highest affinity for Hsc70 from seedling of 1 dag. The characteristics of PTHRHRT is similar to NIVRKKK, which is selected from f2 phage display libraries with bovine Hsc70. These two heptapeptides both possess four basic and positively charged amino acids with high hydrophilicity.