Conformational analysis on the wild type and mutated forms of human ORF1p: a molecular dynamics study

The protein ORF1p, encoded by the LINE-1 retrotransposon, is responsible for the packaging and transposition of its RNA transcript and is reported to be involved in various genetic disorders. The three domains of ORF1p co-ordinate together to facilitate the transposition, and the mechanism of nucleic acid binding is not yet clear. The C-terminal domain of ORF1p adopts a lifted, twisted or rested state, which is regulated by several inter- and intra-domain interactions that are explored in this study. The residues, Glu147, Asp151, Lys154, Arg261 and Tyr282, are majorly involved in mediating the functional dynamics of ORF1p by forming H-bonds and π-interactions. The importance of these residues was elucidated by performing molecular dynamics simulations on both native as well as mutated ORF1p. The Q147A-D151A-K154A mutant expressed unique dynamics featuring the lifting motion of the CTD core alone, while the R261A mutant resulted in the oscillatory motion of CTD. In both cases, the CTDs were held in place by Tyr282 and in its absence, the structural stability of CTDs in the trimeric unit was significantly affected. Additional interactions responsible for stabilizing the trimeric ORF1p to express its native dynamics were extracted in this study. The central role of Tyr282 in maintaining the functional state of ORF1p to facilitate nucleic acid binding and formation of ribonucleoprotein complex is well highlighted. The knowledge gained from this study forms the basis for understanding the nucleic acid binding mechanism of ORF1p, which could further provide additional support in exploring various genetic disorders.