ERICKSON, J.R.; MOERLAND, T.S.; Florida State University; Florida State University: Calcium-binding characteristics of parvalbumin isolated from the Arctic cod (Boreogadus saida)
The calcium-binding protein parvalbumin (PV) is highly abundant in muscle and is thought to sequester intracellular Ca2+ after a contraction, thus facilitating relaxation. The dissociation constant (Kd) of Ca2+ from PV isolated from the Arctic cod (Boreogadus saida) was determined at a suite of temperatures and compared to previously characterized PV from fishes native to temperate and Antarctic waters. PV was isolated by gel permeation and ion exchange chromatography. 2-D PAGE was used to determine sample purity. Kd�s were determined by competition of Ca2+ binding between PV and fluo-3 using a best fit non-linear regression of fluorescence data. Experiments were performed at 0, 5, 15, and 25 �C in 20 mM Hepes buffer (pH 7.2) and 150 mM KCl. Kd strongly varied across the above temperatures, ranging from 4.92 nM at 0 �C to 19.40 nM at 25 �C. The Kd at 5 �C, approximately the native physiological temperature for Boreogadus saida, was found to be 6.68 nM. This value closely matches that of both temperate and Antarctic species at their respective native temperatures, indicating that conservation of this binding characteristic may be an adaptive response to environmental temperature. Supported by NSF IBN-98-08120 and DARPA N66001-02-C-8030
