1H and 17O relaxometric investigations of the binding of Mn(II) ion to human serum albumin

✍ Scribed by Silvio Aime; Simonetta Canton; Simonetta Geninatti Crich; Enzo Terreno

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 209 KB
• Volume: 40
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.974

✦ Synopsis

Abstract

Mn(II) ion binds to human serum albumin (HSA) through one strong binding site (K~A~ = 7.9 × 10^3^ M^−1^) and several weaker binding sites. Through competition assays it has been shown that the strong binding site lies in a region which has been previously identified as the Cd(II) Zn(II) site. The binding of Mn(II) to HSA is strongly pH dependent (p__K__~a~ ≈ 6.7), consistent with the involvement of histidine residues in the coordination of the metal ion. The analysis of ^1^H T~1~ as function of magnetic field strength and of ^17^O T~2~ as function of temperature allowed us to determine the various parameters involved in the relaxation process of the paramagnetic Mn(II) HSA adduct. The Mn(II) ion bound to HSA maintains three or four coordinated water molecules whose residence lifetime is ca 20 ns at 298 K. Interestingly, a good fitting of the NMRD profile was possible only by assuming that the protons of the coordinated water molecules experience two motional regimes, i.e. a fast local motion (probably the rotation around their coordination axis) and the slower overall motion of the whole protein. Copyright © 2001 John Wiley & Sons, Ltd.