Hydrolyzable tannin structures influence relative globular and random coil protein binding strengths.
Binding parameters for the interactions of pentagalloyl glucose (PGG) and four hydrolyzable tannins (representing gallotannins and ellagitannins) with gelatin and bovine serum albumin (BSA) have been determined from isothermal titration calorimetry data. Equilibrium binding constants determined for the interaction of PGG and isolated mixtures of tara gallotannins and of sumac gallotannins with gelatin and BSA were of the same order of magnitude for each tannin (in the range of 10(4)-10(5) M(-1) for stronger binding sites when using a binding model consisting of two sets of multiple binding sites). In contrast, isolated mixtures of chestnut ellagitannins and of myrabolan ellagitannins exhibited 3-4 orders of magnitude greater equilibrium binding constants for the interaction with gelatin (approximately 2 x 10(6) M(-1)) than for that with BSA (approximately 8 x 10(2) M(-1)). Binding stoichiometries revealed that the stronger binding sites on gelatin outnumbered those on BSA by a ratio of at least approximately 2:1 for all of the hydrolyzable tannins studied. Overall, the data revealed that relative binding constants for the interactions with gelatin and BSA are dependent on the structural flexibility of the tannin molecule.
Deaville
Eddie R
ER
Chemistry & Biochemistry Laboratory, Department of Agriculture, University of Reading, Earley Gate, Reading RG6 6AT, United Kingdom.
Green
Rebecca J
RJ
Mueller-Harvey
Irene
I
Willoughby
Ian
I
Frazier
Richard A
RA
D002151:Calorimetry; D005780:Gelatin / Q000737:chemistry*; D047348:Hydrolyzable Tannins / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013816:Thermodynamics
D047348:Hydrolyzable Tannins; D012710:Serum Albumin, Bovine; C435084:pentagalloylglucose; D005780:Gelatin