Disordered Regions in Elongation Factors EF1A in the Three Superkingdoms of Life

摘要

A new criterion proposed for classification of the living world is based on the ability of the protein amino acid sequence to form disordered regions,appearing as loops in the 3D structure.The approach used fundamentally differs from the approaches based on comparisons of certain RNA or protein sequences of different organisms.Introduction of any new structural-functional criterion that could resolve the evolutionary relationships between the main groups of origin organisms is of interest in itself,as megasystematics and macrophy-logeny lack informative criteria despite the apparent abundance of molecular characteristics.The specialized program FoldUnfold was used to search for disordered regions in the elongation factors EF1A (EFs).The reliability of loop prediction was verified against five EFs with the structures known from X-ray analysis.It was demonstrated with the example of several dozens of typical representatives of the living world that the program predicts extra loops in addition to two linkers between three structural domains in EFs.Besides the effector loop,contained in all EFs,six loops were detected at maximum.Of them,three loops (A,B,and C) are in domain I,one (D) is in domain II,and two (E and F) are in domain III.Moreover,all six loops are never present in the same EF.The EF signatures were determined for each of the superkingdoms of life.Each superkingdom displayed variations in the number of loops and their location within the EF domains.Not only the presence of a particular loop was important in the analysis,but also the specificity of its amino acid sequence.As the total number of predicted loops in EFs increases with the increasing complexity of organisms,the following evolutionary role was postulated for the loops.Following the principle of thrifty inventiveness,nature operates with different universal inserts (loops),adapting their number,location within the EF domains,and amino acid composition so that the protein performs specialized functions-single in protozoa and several in higher organisms.