Anti-Obesity Properties of Black Pepper (Piper nigrum): Completing Puzzle using Computational Analysis

Pepper (Piper nigrum) is one of the most common spices found in almost every food. Current knowledge informed that pepper regulates physiological activity in obesity. However, the exact mechanism is still poorly understood. This study determined the potential of piperine and piperidine as major compounds in pepper as GHSR-Ghrelin inhibitors due to over-activity of Ghrelin as appetite hormone in obesity. Molecular docking was performed to simulate the binding pattern of piperine and piperidine as GHSR-Ghrelin antagonist. The result showed that piperidine has a lower potential as GHSR-Ghrelin antagonist than piperine based on binding energy calculation and amino acid interaction. Further, piperine binding to GHSR could shift the Ghrelin binding site to the GHSR. In conclusion, piperine may act as an inhibitor of GHSR-Ghrelin interaction to prevent appetite behavior resulting in bodyweight loss in obesity.

Prokaryotic Argonaute from Archaeoglobus fulgidus interacts with DNA as a homodimer

Argonaute (Ago) proteins are found in all three domains of life. The best-characterized group is eukaryotic Argonautes (eAgos), which are the core of RNA interference. The best understood prokaryotic Ago (pAgo) proteins are full-length pAgos. They are composed of four major structural/functional domains (N, PAZ, MID, and PIWI) and thereby closely resemble eAgos. It was demonstrated that full-length pAgos function as prokaryotic antiviral systems, with the PIWI domain performing cleavage of invading nucleic acids. However, the majority of identified pAgos are shorter and catalytically inactive (encode just MID and inactive PIWI domains), thus their action mechanism and function remain unknown. In this work we focus on AfAgo, a short pAgo protein encoded by an archaeon Archaeoglobus fulgidus. We find that in all previously solved AfAgo structures, its two monomers form substantial dimerization interfaces involving the C-terminal β-sheets. Led by this finding, we have employed various biochemical and biophysical assays, including SEC-MALS, SAXS, single-molecule FRET, and AFM, to show that AfAgo is indeed a homodimer in solution, which is capable of simultaneous interaction with two DNA molecules. This finding underscores the diversity of prokaryotic Agos and broadens the range of currently known Argonaute-nucleic acid interaction mechanisms.