title: Conservation of flexible residue clusters among structural and functional enzyme homologues.
abstract: Conformational flexibility between structural ensembles is an essential component of enzyme function. Although the broad dynamical landscape of proteins is known to promote a number of functional events on multiple time scales, it is yet unknown whether structural and functional enzyme homologues rely on the same concerted residue motions to perform their catalytic function. It is hypothesized that networks of contiguous and flexible residue motions occurring on the biologically relevant millisecond time scale evolved to promote and/or preserve optimal enzyme catalysis. In this study, we use a combination of NMR relaxation dispersion, model-free analysis, and ligand titration experiments to successfully capture and compare the role of conformational flexibility between two structural homologues of the pancreatic ribonuclease family: RNase A and eosinophil cationic protein (or RNase 3). In addition to conserving the same catalytic residues and structural fold, both homologues show similar yet functionally distinct clusters of millisecond dynamics, suggesting that conformational flexibility can be conserved among analogous protein folds displaying low sequence identity. Our work shows that the reduced conformational flexibility of eosinophil cationic protein can be dynamically and functionally reproduced in the RNase A scaffold upon creation of a chimeric hybrid between the two proteins. These results support the hypothesis that conformational flexibility is partly required for catalytic function in homologous enzyme folds, further highlighting the importance of dynamic residue sectors in the structural organization of proteins.
authors.affiliation: Institut National de la Recherche Scientifique-Institut Armand-Frappier, Université du Québec, Laval, Quebec H7V 1B7, Canada.
authors.forename: Donald
authors.initials: D
authors.lastname: Gagné
authors.forename: Laurie-Anne
authors.initials: LA
authors.lastname: Charest
authors.forename: Sébastien
authors.initials: S
authors.lastname: Morin
authors.forename: Evgenii L
authors.initials: EL
authors.lastname: Kovrigin
authors.forename: Nicolas
authors.initials: N
authors.lastname: Doucet
mesh_terms: D000249:Adenosine Monophosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D047150:Eosinophil Cationic Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D012259:Ribonuclease, Pancreatic / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D000249:Adenosine Monophosphate; D047150:Eosinophil Cationic Protein; D012259:Ribonuclease, Pancreatic