After the gut, the mouth is the most important microbiome in the human body, with the inhabitants ranging from bacteria and fungi to viruses and protozoa. If this careful balance of microorganisms is thrown off even by a little, certain pathogens could propagate and cause serious periodontal diseases. One such pathogen is Porphyromonas gingivalis (P. gingivalis), which degrades the specialized basal lamina components that protect supporting teeth tissues. However, one component of this specialized basal lamina, the secretory calcium-binding phosphoprotein proline-glutamine rich 1 (SCPPPQ1) protein, had shown to be not only resistant to P. gingivalis, but also to affect the cell membrane of P. gingivalis itself. A group of researchers then decided to explore the antimicrobial properties of the SCPPPQ1 protein and its peptide derivatives.

SCPPPQ1 protein and peptide derivatives as antibacterial agents

Using the SCPPPQ1 protein itself and derived peptides synthesized by LifeTein, the group sought to test how they fared against P. gingivalis in isolated conditions. After incubating the two together, results showed a rapid and significant decrease of P. gingivalis population. The means of which were narrowed down to aggregation of bacteria and membrane disruption.

The group went further and tested the antibacterial properties against other pathogens, and though there were results, none were as significant as those against P. gingivalis. The results point towards a more honed treatment against P. gingivalis using this knowledge of the SCPPPQ1 protein and its peptide derivatives. Since the protein itself is native to the human mouth, further application to treat periodontal pathogens with its antibacterial properties is not out of the question.

Mary, C., Fouillen, A., Moffatt, P. et al. Effect of human secretory calcium-binding phosphoprotein proline-glutamine rich 1 protein on Porphyromonas gingivalis and identification of its active portions. Sci Rep 11, 23724 (2021). https://doi.org/10.1038/s41598-021-02661-w

Peptide nucleic acids (PNAs) are synthetic mimics of DNA.  The deoxyribose phosphate backbone of PNAs is replaced by a pseudo-peptide polymer. These specific physicochemical properties are exploited to develop a wide range of powerful biomolecular tools, including molecular probes, biosensors, and antigene agents. The PNA molecules can routinely be labeled with biotin, azido, cell penetration peptide fragments, or fluorophores such as FITC, Cy3, Cy5, Cy7, Alexa Dyes, and pyrene.

The uncharged synthetic backbone provides PNA with unique hybridization characteristics. It gives higher stability, or a higher thermal melting temperature (Tm) to the PNA–DNA or PNA–RNA duplexes than the natural homo- or heteroduplexes. In addition, the unnatural backbone of PNAs is not degraded by nucleases or proteases.

It was shown that the binding of PNA to complementary DNA can efficiently block transcriptional elongation and inhibit the binding of transcriptional factors. Thus, the PNAs can be used as antisense or antigene therapeutic agents. PNAs can be used as adapters to link peptides, drugs, or molecular tracers to plasmid vectors. One concept is to form the duplexes of PNAs – cell penetration peptides. The duplexes can penetrate into cells and be used in anticancer applications. The nuclear localization signal (NLS) peptide-PNAs duplexes gave a much higher nuclear localization of a coupled nuclear localization signal than did the free oligonucleotide.

The strategy of PNA-directed PCR clamping is used to inhibit the amplification of a specific target. This PNA–DNA complex formed at one of the primer sites effectively blocks the formation of the PCR product. The procedure can be used to detect single base-pair gene variants for mutation screening and gene isolation. The biotinylated short PNA probes can be used as generic capture probes for the purification of nucleic acids via streptavidin beads. Other applications could be solid-phase hybridization, and fluorescence in situ hybridization (PNA-FISH).

PNA-based applications benefit from the unique Physico-chemical properties of PNA molecules, enabling the development of cell penetration peptide-PNA assays in molecular genetics. 

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