Calcium Binding Properties and Sequence of Frog ( Rana Tegrinka ) Parvalbumin as Determined by Electrospray Ionization-Mass Spectrometry

The primary structure and calcium-binding properties of frog parvalbumin (R. tegrinka, alpha linkage) was determined by using electrospray ionization-mass spectrometry and Edman degradation. A portion of the protein molecules are N-terminally blocked and the blocking group was determined to be an acetyl group by tandem mass spectrometry. The protein contains two cysteines, with one conserved at position 34 and the other located at the C-terminus (residue 110). The protein also dimerizes via a Cys–Cys linkage and binds to one Ca²⁺ with high affinity. An additional Ca²⁺ ion is bound only at high calcium concentration levels. The calcium-binding characteristics for frog parvalbumin are different from those found for rabbit and rat parvalbumins, which bind to two Ca²⁺ ions in a cooperative manner.