ERICKSON, J.R.*; SIDELL, B.D.; MOERLAND, T.S.; Florida State University; University of Maine, Orono; Florida State University: Temperature Sensitivity of Magnesium Affinity for Parvalbumins Isolated from Teleost Fish

Parvalbumin (PV), a small acidic protein expressed abundantly in fast-twitch muscle, can bind two calcium or magnesium ions with high affinity. The dissociation constant (K_D) of Mg²⁺ was measured for PVs isolated from several teleost species spanning a geographic distribution that includes Arctic (Boreogadus saida), Antarctic (Chaenocephalus aceratus and Gobionotothen gibberifrons), and temperate zone waters (Cyprinus carpio and Micropterus salmoides). PV was isolated by gel permeation and ion exchange chromatography. 2-D PAGE and Western blots were used to confirm PV identity. Estimates of K_D were determined by competition of Mg²⁺ binding between PV and Magnesium Green using a best fit non-linear regression of fluorescence data. For all species tested, Mg²⁺ K_D varied across the temperature range 0-25�C. Estimates of K_D for PV from Arctic and Antarctic teleosts were not significantly different at any temperature tested, while K_D values were significantly lower at all temperatures for temperate zone teleosts. However, Mg²⁺ K_D values for all species tested were very similar (0.020-0.025 mM) when examined at their native temperatures (0, 5, and 25�C for Antarctic, Arctic, and temperate zone species, respectively). Our data suggest that magnesium affinity may be conserved for teleost species at their native temperature, possibly reflecting the importance of magnesium binding to parvalbumin function. This work was funded by NSF IBN-9808120 and DARPA N66001-02-C-8030 to TSM, NSF OPP 01-25890 to BDS, and AHA 0415125B to JRE.