title: Resurrecting the ancestral enzymatic role of a modulatory subunit.
abstract: In the post-genomic era, functional prediction of genes is largely based on sequence similarity searches, but sometimes the homologues bear different roles because of evolutionary adaptations. For instance, the existence of enzyme and non-enzyme homologues poses a difficult case for function prediction and the extent of this phenomenon is just starting to be surveyed. Different evolutionary paths are theoretically possible for the loss or acquisition of enzyme function. Here we studied the ancestral role of a model non-catalytic modulatory subunit. With a rational approach, we "resurrected" enzymatic activity from that subunit to experimentally prove that it derived from a catalytic ancestor. We show that this protein (L subunit ADP-glucose pyrophosphorylase) evolved to have a regulatory role, losing catalytic residues more than 130 million years ago, but preserving, possibly as a by-product, the substrate site architecture. Inactivation of catalytic subunits could be the consequence of a general evolutionary strategy to explore new regulatory roles in hetero-oligomers.
authors.affiliation: Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Ballicora
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Dubay
authors.forename: Claire H
authors.initials: CH
authors.lastname: Devillers
authors.forename: Jack
authors.initials: J
authors.lastname: Preiss
mesh_terms: D000244:Adenosine Diphosphate / Q000737:chemistry; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D020134:Catalytic Domain; D003001:Cloning, Molecular; D004247:DNA / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004798:Enzymes / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism; D019143:Evolution, Molecular; D051599:Glucose-1-Phosphate Adenylyltransferase; D007700:Kinetics; D046911:Macromolecular Substances; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009713:Nucleotidyltransferases / Q000737:chemistry* / Q000502:physiology; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
chemical_list: D001426:Bacterial Proteins; D004798:Enzymes; D046911:Macromolecular Substances; D010940:Plant Proteins; D000244:Adenosine Diphosphate; D004247:DNA; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase