Calcium-binding properties and molecular organization of bradykinin A solution 1H-NMR study.
The NMR features of bradykinin were investigated in dimethylsulfoxide containing 1% water. The temperature dependence of chemical shifts and ROESY maps were monitored for the major species where all X-Pro bonds are trans. The occurrence of a head-to-tail ionic interaction and intramolecular hydrogen bonds stabilizing a pseudo cyclic arrangement was inferred, a beta turn at the C-terminus being the main feature of the secondary structure. Calcium was shown to bind to the peptide with a dissociation constant Kd = 2.8 + 0.2 mm. 2Pro and 3Pro carbonyls, as well as the 9Arg carboxyl, were assigned as the metal-binding sites. A molecular model of the 1 : 1 metal-complex was obtained. In light of conformational changes experienced by the peptide upon interaction with calcium, a role for the metal was hypothesized in the process of conformational selection from the free to the receptor-bound state of bradykinin.
Gaggelli
E
E
Department of Chemistry, University of Sienna, Italy. Gaggelli@unisi.it
D'amelio
N
N
MacCotta
A
A
Valensin
G
G
D001920:Bradykinin / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011485:Protein Binding; D011522:Protons
D011522:Protons; D001920:Bradykinin; D002118:Calcium