title: Carbohydrate affinity for the glucose-galactose binding protein is regulated by allosteric domain motions.
abstract: Protein function, structure, and dynamics are intricately correlated, but studies on structure-activity relationships are still only rarely complemented by a detailed analysis of dynamics related to function (functional dynamics). Here, we have applied NMR to investigate the functional dynamics in two homologous periplasmic sugar binding proteins with bidomain composition: Escherichia coli glucose/galactose (GGBP) and ribose (RBP) binding proteins. In contrast to their structural and functional similarity, we observe a remarkable difference in functional dynamics: For RBP, the absence of segmental motions allows only for isolated structural adaptations upon carbohydrate binding in line with an induced fit mechanism; on the other hand, GGBP shows extensive segmental mobility in both apo and holo states, enabling selection of the most favorable conformation upon carbohydrate binding in line with a population shift mechanism. Collective segmental motions are controlled by the hinge composition: by swapping two identified key residues between RBP and GGBP we also interchange their segmental hinge mobility, and the doubly mutated GGBP* no longer experiences changes in conformational entropy upon ligand binding while the complementary RBP* shows the segmental dynamics observed in wild-type GGBP. Most importantly, the segmental interdomain dynamics always increase the apparent substrate affinity and thus, are functional, underscoring the allosteric control that the hinge region exerts on ligand binding.
authors.affiliation: Structural Biology Unit, CIC bioGUNE, Bizkaia Technology Park, Building 800, 48160 Derio, Spain.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Ortega
authors.forename: David
authors.initials: D
authors.lastname: Castaño
authors.forename: Tammo
authors.initials: T
authors.lastname: Diercks
authors.forename: Oscar
authors.initials: O
authors.lastname: Millet
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D002151:Calorimetry; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D005947:Glucose / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D033902:Periplasmic Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
chemical_list: D002135:Calcium-Binding Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; C023550:galactose-binding protein; D005947:Glucose