Unraveling a natural protease inhibitor from marine Streptomyces griseoincarnatus HK12 active against Chikungunya virus

Proteases play an indispensable role in the life cycles of several life-threatening organisms such as the ones causing malaria, cancer and AIDS. A targeted blockade of these enzymes could be an efficient approach for drug modeling against these causative agents. Our study was directed towards the extraction and characterization of a protease inhibitor having activity against Chikungunya virus (CHIKV). A protein-based protease inhibitor (PI) in Streptomyces griseoincarnatus HK12 with anti-viral activity against CHIKV was revealed when screened against two major proteases, papain and trypsin. The PI was efficiently extracted at 60 % ammonium sulfate saturation and purified by ion-exchange chromatography (CM-Sepharose) at 300 mM NaCl elution followed by SDS-PAGE (10 %). The protein was characterized by denaturing SDS-PAGE, reverse zymography, and MALDI-TOF peptide mass fingerprinting. The protein-based PI was studied to have a high molecular weight of 66−70 kDA. The PI was tested to supress the supress cytopathic effects (CPE) exerted by the clinically isolated virus in BHK21 cells. This was used as a measure to determine the antiviral activity. The PI exerted significant effects with an effective concentration calculated as EC50 11.21 μg/mL. The protein was found to be reported as the first of its kind which also stands out to be the first a natural protease inhibitor against the treatment of the chikungunya virus.