title: Cation binding to parvalbumin studied by 113Cd and 23Na NMR. Peak assignment of rabbit (pI 5.5) parvalbumin.
abstract: Cation binding to three apoparvalbumins was studied by means of 113Cd NMR. The 3 parvalbumins that were investigated were carp pI 4.25, rabbit pI 5.5 and pike pI 5.0. The results showed that Cd2+ ions bind to the EF and CD sites of carp apoparvalbumin pI 4.25 with about the same affinity. For rabbit (pI 5.5) apoparvalbumin, Cd2+ binds preferentially to the EF site, while for pike (pI 5.0) apoparvalbumin, it was the CD site that exhibited somewhat higher affinity for Cd2+. The effect of Mn2+ on the 113Cd signals of rabbit parvalbumin was used to assign the 113Cd NMR signals to the EF and CD sites. The Mn2+ paramagnetic effect on rabbit and pike parvalbumins differed from that obtained for carp parvalbumin. This is in agreement with the assumption that the beta-lineage parvalbumins possess a third external site of higher affinity than the alpha-lineage parvalbumins. Furthermore, 23Na NMR was used to study Na+-Mg2+ competition in the native carp (pI 4.25) parvalbumin. The results showed that Na+ and Mg2+ compete for the same site, the third external site.
mesh_terms: D000818:Animals; D002104:Cadmium; D002412:Cations; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008345:Manganese / Q000494:pharmacology; D009124:Muscle Proteins / Q000378:metabolism*; D010320:Parvalbumins / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D012964:Sodium
chemical_list: D002412:Cations; D009124:Muscle Proteins; D010320:Parvalbumins; D002104:Cadmium; D008345:Manganese; D012964:Sodium