To develop novel antibiotic peptides useful as therapeutic drugs, the enantiomeric analogue of pleurocidin (Ple), which is a well known 25-mer antimicrobial peptide, was designed for proteolytic resistance by D-amino acids substitution. The proteolytic resistance was confirmed by using HPLC after the digestion with various proteases. To investigate the antibiotic effect of L- and D-Ple, the antibacterial activity and hemolytic effect were tested against human erythrocytes. The D-Ple showed a decreased antibacterial activity and a dramatically decreased hemolytic activity compared with L-Ple. The hemolytic effect of analogue was further confirmed by using calcein leakage measurement with liposome. To elucidate these results, the secondary structure of the peptides was investigated by using circular dichroism spectroscopy. The results revealed that D-Ple, as well as L-Ple, had typical ?-helical structures which were mirror images, with a different helicity. These results suggested that the discrepancy of the structure between the two peptides made their antibacterial activity distinct.
Anti-Infective Agents/*chemistry/*pharmacology ; Erythrocytes/drug effects ; Fish Proteins/*chemistry/*pharmacology ; Gram-Negative Bacteria/drug effects ; Gram-Positive Bacteria/drug effects ; Hemolytic Agents/chemistry/pharmacology ; Humans ; Microbial Sensitivity Tests ; Stereoisomerism ; Structure-Activity Relationship

Arg-Gly-Asp (RGD)-toxin protein Lj-RGD3 of Lampetra japonica shares homologous with a Histidine-rich glycoprotein (HRG), and both RGD-toxin protein and HRG have antiangiogenic activities with different targets. To study the relationship between the function and the structure of Lj-RGD3, we studied the anti-angiogenic characteristics of both Lj-RGD3 and the mutation named Lj-112 of which three RGD motifs of Lj-RGD3 were deleted. We synthesized the gene of Lj-112, constructed it to the plasmid pET23b, and expressed the recombinant proteins in Escherichia coli BL21. Both recombinant proteins with the C-terminal his-tag were 15 kDa soluble proteins. Then we purified rLj-RGD3 and rLj-112 using the His-Bind affinity chromatography. To examine the effect of both proteins on bFGF-induced proliferation of ECV304 cell, we carried out the 3-(4,5)-dimethylthiahiazo (-z-yl)-3,5-di-phenytetrazoliumromide (MTT) assays. For cell migration and invasion assays, we used Transwell containing insert filter and Matrigel to imitate the in vivo environment. To examine whether both proteins were capable of interrupting the angiogenesis in vivo, we used the chick chicken embryonic chorioallantoic membrane (CAM) as an angiogenesis model. We used Integrin-linked kinase1 (ILK1) ELISA method to study functionary mechanisms of rLj-RGD3 and rLj-112. Both rLj-RGD3 and rLj-112 inhibited bFGF-induced proliferation of ECV304 cells in a dose-dependent manner with IC50 at 0.889 micromol/L and 0.160 micromol/L, respectively. The results of migration and invasion assays revealed that both rLj-RGD3 and rLj-112 showed significant inhibition on bFGF induced migration and invasion of ECV304; and rLj-112 was more active than rLj-RGD3. The result of CAM angiogenesis assay demonstrated that both proteins inhibited the angiogenesis in chick CAM, and rLj-112 was more active than rLj-RGD3. ELISA assay of ILK1 showed that both rLj-RGD3 and rLj-112 down-regulated ILK1 expression of ECV304 cell. The fact of rLj-112 was more active than rLj-RGD3 on anti-angiogenesis indicate that rLj-112 was likely with histidine-rich glycoprotein (HRG), and the factor of sequence homologous between rLj-RGD3 and HRG cannot enhance antiangiogenic activities of rLj-RGD3, the signal pathway of anti-angiogenesis of rLj-RGD3 and rLj-112 are differently.
Amino Acid Sequence ; Angiogenesis Inhibitors ; pharmacology ; Animals ; Base Sequence ; Cell Line ; Fish Venoms ; biosynthesis ; genetics ; isolation & purification ; pharmacology ; Humans ; Lampreys ; metabolism ; Molecular Sequence Data ; Mutant Proteins ; chemistry ; pharmacology ; Oligopeptides ; biosynthesis ; genetics ; isolation & purification ; pharmacology

Lj-RGD3 was a toxin from the saliva gland of Lampetra japonica. To study the anti-tumor function of rLj-RGD3 and confirm its biological status and significance, we extracted total RNA from the saliva gland and amplified the cDNA of Lj-RGD3 by RT-PCR. The cDNA of Lj-RGD3 was 357 bp long and encoded a polypeptide composed of 118 amino acids including 2 cysteines, 17 histidines and 3 RGD (Arg-Gly-Asp) motifs. We cloned the cDNA into the plasmid pET23b, and expressed the recombinant protein rLj-RGD3 in Escherichia coli BL21. Fusion rLj-RGD3 with the C-terminal his-tag was a 15 kD soluble protein. Using the His-Bind affinity chromatography, we purified rLj-RGD3. Furthermore, we determined the biological activities of rLj-RGD3. To examine the ability of rLj-RGD3 inhibiting Hela cells proliferation, we used MTT assay. The results showed that, rLj-RGD3 inhibited bFGF induced proliferation of Hela cells in a dose-dependent manner, the IC50 value was 2.6 micromol/L. Hoechst staining assay revealed that, the nuclei of the cells treated with rLj-RGD3 were stained much brighter than that of untreated cells due to chromatin condensation. Furthermore, the DNA ladder patterns from the cells treated with rLj-RGD3 were also observed. These results demonstrated that rLj-RGD3 could induce apoptosis of Hela cells. Cell adhesion, migration and invasion are critical processes in tumor metastasis. rLj-RGD3 significantly inhibited adhesion of Hela cells to vironectin in a dose-dependent manner. In order to determine the effect of rLj-RGD3 on Hela cells migration toward bFGF, we used Transwell containing insert filter. rLj-RGD3 showed a significant inhibition on Hela cells migration, the inhibition rate was 60%. In the invasion assay, the Matrigel and Transwell were used to imitate environment in vivo. The results of invasion assay revealed that, rLj-RGD3 significantly inhibited bFGF induced invasion of Hela cells. Taken together, these results revealed that rLj-RGD3 had typical functions of RGD toxin protein and will be valuable in developing anti-tumor recombinant medicine.
Amino Acid Sequence ; Animals ; Antineoplastic Agents ; pharmacology ; Apoptosis ; drug effects ; Female ; Fish Venoms ; biosynthesis ; genetics ; isolation & purification ; pharmacology ; HeLa Cells ; Humans ; Lampreys ; metabolism ; Molecular Sequence Data ; Oligopeptides ; biosynthesis ; genetics ; isolation & purification ; pharmacology ; Recombinant Proteins ; biosynthesis ; genetics ; pharmacology ; Salivary Glands ; chemistry