Search

We tested whether model peptides for group 3 late embryogenesis abundant (G3LEA) proteins, which we developed previously, are capable of maintaining the catalytic activities of enzymes dried in their presence. Three different peptides were compared: 1) PvLEA-22, which consists of two tandem repeats of the 11-mer motif found in G3LEA proteins from an African sleeping chironomid; 2) PvLEA-44, which is made of four tandem repeats of the same 11-mer motif; and 3) a peptide whose amino acid composition is the same as that of PvLEA-22, but whose sequence is scrambled. We selected two enzymes, lactate dehydrogenase (LDH) and β-d-galactosidase (BDG), as targets because they have different isoelectric point (pI) values, in the alkaline and acidic range, respectively. While these enzymes were almost inactivated when dried alone, their catalytic activity was preserved at ≥70% of native levels in the presence of any of the above three peptides. This degree of protection is comparable to that conferred by several full-length G3LEA proteins, as reported previously for LDH. Interestingly, the protective activity of the peptides was enhanced slightly when they were mixed with trehalose, especially when the molar content of the peptides was low. On the basis of these results, the G3LEA model peptides show promise as protectants for the dry preservation of enzymes/proteins with a wide range of pI values., (Copyright © 2016 Elsevier B.V. All rights reserved.)

We investigated whether a model peptide for group 3 LEA (G3LEA) proteins we developed in previous studies can protect liposomes from desiccation damage. Four different peptides were compared: 1) PvLEA-22, which consists of two tandem repeats of the 11-mer motif characteristic of LEA proteins from the African sleeping chironomid; 2) a peptide with amino acid composition identical to that of PvLEA-22, but with its sequence scrambled; 3) poly-l-glutamic acid; and 4) poly-l-lysine. Peptides 1) and 2) protected liposomes composed of 1-palmitoyl 2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) against fusion caused by desiccation, as revealed by particle size distribution measurements with dynamic light scattering. Indeed, liposomes maintain their pre-stress size distribution when these peptides are added at a peptide/POPC molar ratio of more than 0.5. Interestingly, peptide 1) achieved the comparable or higher retention of a fluorescent probe inside liposomes than did several native LEA proteins published previously. In contrast, the other peptides exhibited less protective effects. These results demonstrate that the synthetic peptide derived from the G3LEA protein sequence can suppress desiccation-induced liposome fusion. Fourier transform infrared (FT-IR) spectroscopic measurements were performed for the dried mixture of each peptide and liposome. Based on results for the gel-to-liquid crystalline phase transition temperature of the liposome and the secondary structure of the peptide backbone, we discuss possible underlying mechanisms for the protection effect of the synthetic peptide on dried liposomes., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Group 3 late embryogenesis abundant (G3LEA) proteins have amino acid sequences with characteristic 11-mer motifs and are known to reduce aggregation of proteins during dehydration. Previously, we clarified the structural and thermodynamic properties of the 11-mer repeating units in G3LEA proteins using synthetic peptides composed of two or four tandem repeats originating from an insect (Polypedilum vanderplanki), nematodes and plants. The purpose of the present study is to test the utility of such 22-mer peptides as protective reagents for aggregation-prone proteins. For lysozyme, desiccation-induced aggregation was abrogated by low molar ratios of a 22-mer peptide, PvLEA-22, derived from a P. vanderplanki G3LEA protein sequence. However, an unexpected behavior was noted for the milk protein, α-casein. On drying, the resultant aggregation was significantly suppressed in the presence of PvLEA-22 with its molar ratios>25 relative to α-casein. However, when the molar ratio was <10, aggregation occurred on addition of PvLEA-22 to aqueous solutions of α-casein. Other peptides derived from nematode, plant and randomized G3LEA protein sequences gave similar results. Such an anomalous solubility change in α-casein was shown to be due to a pH shift to ca. 4, a value nearly equal to the isoelectric point (pI) of α-casein, when any of the 22-mer peptides was mixed. These results demonstrate that synthetic peptides derived from G3LEA protein sequences can reduce protein aggregation caused both by desiccation and, at high molar ratios, also by pH effects, and therefore have potential as stabilization reagents., (Copyright © 2012 Elsevier B.V. All rights reserved.)