We have studied protein L1 from halophilic archaea Haroarcula marismortui . The protein is rRNA-binding and interacts with helices Н77-Р78 of the 23S rRNA. We introduced a stabilizing disulphide bridge in the structure of protein L1. To identify the region in the polypeptide chain where the SS-bridge should be inserted, we used the approach based on the search for intrinsically disordered regions in proteins. The results of our previous study [1] confirmed that the software for prediction of intrinsically disordered regions, for example, PONDR-FIT and IsUnstruct, can be employed for identification of weakened regions in proteins with rigid packing. Such regions are most suitable to insert stabilizing disulphide bridges. Using software PONDR-FIT and IsUnstruct we analyzed the amino acid sequence of protein L1 and predicted the region with a high structural irregularity. It is the region in the second domain of the protein. We chose amino acid residues E82 and D114 in the predicted region, the substitution of which for cysteine residues resulted in the formation of the desired disulphide bridge. Using the method of circular dichroism spectroscopy it was demonstrated that the introduced disulphide bridge increased the melting temperature of protein L1 by approximately 10 degrees.
ribosomal protein L1, Haroarcula marismortui, disulphide bond, protein stability, intrinsic disorder regions, circular dichroism spectroscopy
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