Lead-207 NMR: a novel probe for the study of calcium-binding proteins

摘要: The high-affinity Ca2+–binding sites of carp (pI 4.25) and pike 5.0) parvalbumins, as well those mammalian calmodulin (CaM) its C-terminal tryptic half-molecule (TR2C), were analyzed by 207Pb NMR spectroscopy. For the two signals observed ranging in chemical shift from ≈750 to ≈1260 ppm downfield aqueous Pb(NO3)2, corresponding 207Pb2+ bound helix-loop-helix each these proteins. Four signals, which fall same window, could be discerned for CaM. Experiments on TR2C permitted assignment signal due occupying a site either N- or C-lobe intact protein. 1H titration studies CaM provided evidence that Pb2+ binding all four occurs simultaneously, contrast behavior this protein presence Ca2+. Titrations 207Pb2+–forms with antipsychotic drug trifluoperazine demonstrated exposed hydrophobic surfaces causes substantial conformational changes proceeds sequential manner – first subsequently N-lobe. Finally, field dependence CaM-bound was examined. linewidths exhibited sharp square external magnetic field, trend characteristic relaxation via anisotropy. Relaxation exchange also contributes linewidths. large dispersion three proteins studied here illustrates remarkable sensitivity parameter subtle differences environment protein-bound nucleus. To our knowledge, data presented article comprise ever published example application spectroscopy metalloproteins.