Meeting Abstract

P2.73A  Friday, Jan. 4  Parvalbumin in Fish Muscle: Characterization of Binding Properties and Role in Muscle Relaxation SOLOMON, S.; SIROHI, M.; BASTIN, L. D.; COUGHLIN, D. J.*; Widener University, Chester, PA; Widener University, Chester, PA; Widener University, Chester, PA; Widener University, Chester, PA djcoughlin@widener.edu

Parvalbumin (PV), a myoplasmic protein with multiple isoforms in fish muscle, is a low molecular weight protein (9-11 kD) that appears to aid in relaxation from contraction. PV binds free Ca²⁺, which reduces the intracellular concentration of the ion and leads to muscle relaxation. The diverse isoforms of PV appear to have different impacts on relaxation, perhaps because of variations in the cation binding properties of each isoform. We report on two approaches to study the influence of PV on fish muscle relaxation. First, mechanics measurements of muscle relaxation were carried out in conjunction with protein analysis of PV expression in rainbow trout muscle. There is a correlation between muscle relaxation and the total amount of PV as well as the relative expression of two PV isoforms (Parv1 and Parv2). Trout muscle with high relaxation rates expresses more PV and relatively more of the Parv2 isoform. Second, we characterized PV cation (Ca²⁺ and Mg²⁺) binding characteristics. Since PV is bound to Mg²⁺ in its native state, Mg²⁺ ions must dissociate for PV to bind Ca²⁺ ions. Therefore, the dissociation rate for Mg²⁺ is believed to determine the physiological properties of PV and its ability to aid in relaxation. Our physiology results suggest that there are differences in the Ca²⁺ and Mg²⁺ binding by the two isoforms of PV. To test this suggestion, we have isolated and purified the two isoforms of PV from fish muscle (sheepshead and rainbow trout) using gel filtration and anion-exchange chromatography. Competitive fluorescence assays indicate differential calcium binding by the PV isoforms in fish. We also report on the first measurements of Mg²⁺ dissociation in fish PV.