Structural studies of calcium-binding proteins using nuclear magnetic resonance

Lanthanide-shifted 1H nuclear magnetic resonance (NMR) spectroscopy has been used to compare the structure in solution of the EF-hand calcium-binding domains of four parvalbumins (isoelectric pH[pI] 3.95, 4.25, and 4.37 from carp, and pI from buffalo fish). These four parvalbumins are shown by NMR to have very similar structures at the level of resolution typical of x-ray structures. At the higher resolution possible by the lanthanide NMR technique, specific differences are noted between the pI 3.95 isoprotein from carp and the other two carp isoproteins, and the buffalo fish parvalbumin is shown to be different from all three carp isoproteins. The differences are estimated to correspond to changes of the order of 0.2 A in the positions of some of the nuclei surrounding the EF calcium site