title: A despecialization step underlying evolution of a family of serine proteases.
abstract: In the trypsin superfamily of serine proteases, non-trypsin-like primary specificities have arisen in only two monophyletic descendent subbranches. We have recreated an ancestor to one of these subbranches (granzyme) using phylogenetic inference, gene synthesis, and protein expression. This ancestor has two unusual properties. First, it has broad primary specificity encompassing the entire repertoire of novel primary specificities found in its descendents. Second, unlike extant members that have narrow primary specificities, the ancestor exhibits tolerance to mutational changes in primary specificity-conferring residues-that is, structural plasticity. Molecular modeling and mutagenesis studies indicate that these unusual properties are due to a particularly wide substrate binding pocket. These two crucial properties of the ancestor not only distinguish it from its extant descendents but also from the trypsin-like proteases that preceded it. This indicates that a despecialization step, characterized by broad specificity and structural plasticity, underlies evolution of new primary specificities in this protease superfamily.
authors.affiliation: Victor Chang Cardiac Research Institute, Sydney, New South Wales 2010, Australia.
authors.forename: Merridee A
authors.initials: MA
authors.lastname: Wouters
authors.forename: Ke
authors.initials: K
authors.lastname: Liu
authors.forename: Peter
authors.initials: P
authors.lastname: Riek
authors.forename: Ahsan
authors.initials: A
authors.lastname: Husain
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002384:Catalysis; D002918:Chymotrypsin / Q000737:chemistry; D019143:Evolution, Molecular; D053804:Granzymes; D007700:Kinetics; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010649:Phenylalanine / Q000737:chemistry; D010802:Phylogeny; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011485:Protein Binding; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism*; D012756:Sheep; D013379:Substrate Specificity; D013997:Time Factors; D014357:Trypsin / Q000737:chemistry / Q000494:pharmacology
chemical_list: D011994:Recombinant Proteins; D010649:Phenylalanine; D053804:Granzymes; C509214:Gzmb protein, mouse; C509215:Gzmb protein, rat; D012697:Serine Endopeptidases; D002918:Chymotrypsin; D014357:Trypsin