title: Can an arbitrary sequence evolve towards acquiring a biological function?
abstract: To explore the possibility that an arbitrary sequence can evolve towards acquiring functional role when fused with other pre-existing protein modules, we replaced the D2 domain of the fd-tet phage genome with the soluble random polypeptide RP3-42. The replacement yielded an fd-RP defective phage that is six-order magnitude lower infectivity than the wild-type fd-tet phage. The evolvability of RP3-42 was investigated through iterative mutation and selection. Each generation consists of a maximum of ten arbitrarily chosen clones, whereby the clone with highest infectivity was selected to be the parent clone of the generation that followed. The experimental evolution attested that, from an initial single random sequence, there will be selectable variation in a property of interest and that the property in question was able to improve over several generations. fd-7, the clone with highest infectivity at the end of the experimental evolution, showed a 240-fold increase in infectivity as compared to its origin, fd-RP. Analysis by phage ELISA using anti-M13 antibody and anti-T7 antibody revealed that about 37-fold increase in the infectivity of fd-7 was attributed to the changes in the molecular property of the single polypeptide that replaced the D2 domain of the g3p protein. This study therefore exemplifies the process of a random polypeptide generating a functional role in rejuvenating the infectivity of a defective bacteriophage when fused to some preexisting protein modules, indicating that an arbitrary sequence can evolve toward acquiring a functional role. Overall, this study could herald the conception of new perspective regarding primordial polypeptides in the field of molecular evolution.
authors.affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, 565-0871, Suita City, Osaka, Japan.
authors.forename: Yuuki
authors.initials: Y
authors.lastname: Hayashi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sakata
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Makino
authors.forename: Itaru
authors.initials: I
authors.lastname: Urabe
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yomo
mesh_terms: D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000235:genetics* / Q000502:physiology; D001483:Base Sequence; D036022:Capsid Proteins; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000821:virology; D019143:Evolution, Molecular; D015723:Gene Library; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000235:genetics* / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012641:Selection, Genetic; D013753:Tetracycline Resistance / Q000235:genetics; D014760:Viral Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D036022:Capsid Proteins; D004268:DNA-Binding Proteins; D010455:Peptides; D011993:Recombinant Fusion Proteins; D014760:Viral Fusion Proteins