In silico and in vitro analysis about effects of the affinity tags on the rate of amyloid fibrilation of proteins

Nowadays, study on the abnormal protein aggregation has been interested by researchers in different areas of science especially medicine and biotechnology. The aggregated amyloid fibrils of proteins play the major role in several important diseases including Alzheimer’s’, Parkinson’s’ and type II diabetes. In biotechnology, a major problem during production and purification of the recombinant proteins and peptides is the formation of irreversible aggregates. In the recombinant proteins some tags are usually added in the C-terminal or N-terminal of the genes which can change the physicochemical properties of proteins. So far, no comprehensive study has been carried out on the effect of these sequences on the aggregation of recombinant proteins. In this study, by using AGGRESCAN bioinformatics algorithm, the effect of different tags on propensity of the aggregation of recombinant proteins was investigated. Results demonstrated that the tags can affect the protein aggregation. To determine accuracy of in silico prediction, the fibrillation of alpha-synuclein with or without His-tag was assessed by circular dichroism, atomic force microscopy, fluorimetry and the amyloid standard tests. Alpha-synuclein is the key protein in the development of neurodegenerative diseases by formation the extensive plaques. The bioinformatics program predicted that His-tag can induce the protein tendency to aggregation. Data obtained from experimental study also confirmed the in silico results and showed that the presence of the tag inspire the fibrillation process in alpha-synuclein. Thus it is suggested in many studies, especially studies related to the pathogenesis of fibrillation or exploring the inhibitors of protein aggregation such tags removed from proteins.