title: Evolution of structure and function in the o-succinylbenzoate synthase/N-acylamino acid racemase family of the enolase superfamily.
abstract: Understanding how proteins evolve to provide both exquisite specificity and proficient activity is a fundamental problem in biology that has implications for protein function prediction and protein engineering. To study this problem, we analyzed the evolution of structure and function in the o-succinylbenzoate synthase/N-acylamino acid racemase (OSBS/NAAAR) family, part of the mechanistically diverse enolase superfamily. Although all characterized members of the family catalyze the OSBS reaction, this family is extraordinarily divergent, with some members sharing <15% identity. In addition, a member of this family, Amycolatopsis OSBS/NAAAR, is promiscuous, catalyzing both dehydration and racemization. Although the OSBS/NAAAR family appears to have a single evolutionary origin, no sequence or structural motifs unique to this family could be identified; all residues conserved in the family are also found in enolase superfamily members that have different functions. Based on their species distribution, several uncharacterized proteins similar to Amycolatopsis OSBS/NAAAR appear to have been transmitted by lateral gene transfer. Like Amycolatopsis OSBS/NAAAR, these might have additional or alternative functions to OSBS because many are from organisms lacking the pathway in which OSBS is an intermediate. In addition to functional differences, the OSBS/NAAAR family exhibits surprising structural variations, including large differences in orientation between the two domains. These results offer several insights into protein evolution. First, orthologous proteins can exhibit significant structural variation, and specificity can be maintained with little conservation of ligand-contacting residues. Second, the discovery of a set of proteins similar to Amycolatopsis OSBS/NAAAR supports the hypothesis that new protein functions evolve through promiscuous intermediates. Finally, a combination of evolutionary, structural, and sequence analyses identified characteristics that might prime proteins, such as Amycolatopsis OSBS/NAAAR, for the evolution of new activities.
authors.affiliation: Department of Biopharmaceutical Sciences, University of California, San Francisco, CA 94143, USA.
authors.forename: Margaret E
authors.initials: ME
authors.lastname: Glasner
authors.forename: Nima
authors.initials: N
authors.lastname: Fayazmanesh
authors.forename: Ranyee A
authors.initials: RA
authors.lastname: Chiang
authors.forename: Ayano
authors.initials: A
authors.lastname: Sakai
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Jacobson
authors.forename: John A
authors.initials: JA
authors.lastname: Gerlt
authors.forename: Patricia C
authors.initials: PC
authors.lastname: Babbitt
mesh_terms: D039903:Actinobacteria / Q000201:enzymology; D000581:Amidohydrolases / Q000737:chemistry*; D000595:Amino Acid Sequence; D001499:Bayes Theorem; D019755:Carbon-Carbon Lyases / Q000737:chemistry*; D019143:Evolution, Molecular; D023281:Genomics; D008969:Molecular Sequence Data; D010751:Phosphopyruvate Hydratase / Q000737:chemistry*; D010802:Phylogeny; D019998:Racemases and Epimerases / Q000737:chemistry*; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D024482:Vitamin K 2 / Q000737:chemistry
chemical_list: D024482:Vitamin K 2; D000581:Amidohydrolases; C032846:alpha-N-acylamino acid hydrolase; D019755:Carbon-Carbon Lyases; C052986:o-succinylbenzoic acid synthase; D010751:Phosphopyruvate Hydratase; D019998:Racemases and Epimerases