Tannin interactions with a full-length human salivary proline-rich protein display a stronger affinity than with single proline-rich repeats.
The protein IB5 has been purified from human parotid saliva. This protein contains several repeats of a short proline-rich sequence. Dissociation constants have been measured at several discrete binding sites using 1H-NMR for the hydrolysable tannins (polyphenols) beta-1,3,6-tri-O-galloyl-D-glucopyranose, beta-1,2,4,6-tetra-O-galloyl-D-glucopyranose and beta-1,2,3,4,6-penta-O-galloyl-D-glucopyranose and the condensed proanthocyanidin (--)-epicatechin. The dissociation constants for trigalloyl glucose and pentagalloyl glucose were 15 X 10(-5) and 1.7 X 10(-5) M, respectively, which are 115 and 1660 times stronger than those previously measured under the same conditions for a single repeat of a mouse salivary proline-rich protein. The increase in affinity is ascribed to intramolecular secondary interactions, which are strengthened by the rigidity of the interacting molecules.
Charlton
A J
AJ
Department of Molecular Biology and Biotechnology, The Krebs Institute for Biomolecular Research, University of Sheffield, Sheffield, UK.
Baxter
N J
NJ
Lilley
T H
TH
Haslam
E
E
McDonald
C J
CJ
Williamson
M P
MP
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002392:Catechin / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D010306:Parotid Gland / Q000737:chemistry; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*; D055232:Proline-Rich Protein Domains; D011485:Protein Binding; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D017421:Sequence Analysis; D013634:Tannins / Q000378:metabolism*
D000596:Amino Acids; D010455:Peptides; D012471:Salivary Proteins and Peptides; D013634:Tannins; D002392:Catechin; D011392:Proline