To develop an efficient protein expression system, we designed a late embryogenesis abundant (LEA) peptide by mutating the LEA peptide constructed in our previous study (LEA-I). The peptide is based on the repeating units of an 11mer motif characteristic of LEA proteins from Polypedilum vanderplanki larvae. In the amino acid sequence of the 13mer LEA peptide, glycine at the 6th and 12th positions was replaced with other amino acids via point mutations. Glutamic acid, lysine, leucine, and asparagine in the LEA peptide at the 6th and 12th positions increased green fluorescence protein (GFP) expression. The GFP expression of the mutated LEA peptide was 1.5 to 2.0 times higher than that without LEA peptide. In contrast, the serine-containing mutated LEA peptide has low GFP expression levels. We hypothesize that the position of amino acids and the nature of amino acid in LEA peptide are important for our coexpression system. These data suggest that the size, structure, and charge of amino acids in the LEA peptide improve the protection and expression of the target protein. The amino acid balance also plays an important role in the expression of the target protein.

Formal synthesis of teadenol A and B was achieved via Pd-catalyzed 6-endo cyclization of phenol having vinylepoxide moiety as a key reaction. Although 5-exo and 6-endo cyclizations compete for the cyclization of epoxides with a nucleophilic moiety at the 5-position, 6-endo cyclization can be realized by using a palladium catalyst.