Design and expression of high nutritional peptide (HEAAE) in E-coli

A novel protein (HEAAE, High Essential Amino Acid Encoding Protein), rich in essential amino acids (75% of total), was designed and constructed in our laboratory. The designed peptides were analyzed by SYBLE and stable secondary and tertiary structures were predicted. The monomeric form (HEAAE-1) of the protein consists of 20 amino acid residues with four additional amino acids comprising a potential beta-turn (HEAAE-4). Size exclusion analysis demonstrated that the monomer is self-aggregates in aqueous solution to form higher ordered multimeric structures, which are very reminiscent of natural plant storage proteins. The DNA, encoding this amino acid sequence was synthesized, and from this monomeric gene fragment (heaae-1), the stable tetrameric form of the gene (heaae-4) was generated by subcloning into the E. coli expression vector pKK223-3. A clear 6 kDa polypeptide band corresponding to the molecular weight of the dimeric form (HEAAE-2) was detected. The smeared band which appeared around the molecular weight corresponding to HEAAE-4 of II kDa suggested that the tetramer form of this protein might be processed into smaller size products.