Proteins are vital to many functions of biological organisms including muscle relaxation and antifreeze activity. It is known that the structure of a protein is an important component of the control mechanism. We are characterizing proteins isolated from the muscles of fish to understand how proteins control various processes.

The physiological properties of muscle are highly dependent on the various isoforms of several muscle proteins. Parvalbumin, a myoplasmic protein with two isoforms aids in relaxation by releasing Mg(II) and binding free Ca(II) which reduces the intracellular concentration of the ion. Since calcium plays a necessary role in contraction by binding to the regulatory protein troponin, a decrease in its intracellular concentration will result in relaxation of the muscle fiber. Although studies have shown differences in the Ca(II) dissociation constant (K_D) for parvalbumin from different fish species, there is presently no data on how Ca(II) and Mg(II) dissociation rates might vary between isoforms of a given fish species. To address this issue, we are studying the Ca(II) and Mg(II) binding characteristics of parvalbumin isoforms in sheepshead, rainbow trout, rainbow smelt, and black tip reef shark. Here we report on our isolation and characterization of two isoforms of parvalbumin from sheepshead and rainbow trout.

Many organisms are able to survive at nearly subzero temperatures where bodily fluids are normally susceptible to freezing. Consequently, numerous organisms have adapted to these temperatures by synthesizing antifreeze proteins, proteins capable of binding to ice thus making further ice crystal growth energetically unfavorable, which allows the organism to endure harsher conditions. We are studying the muscle proteins of smelt in order to elucidate the mechanism by which the protein(s) exerts control over ice nucleation.