Meeting Abstract
P1.125 Thursday, Jan. 3 Do counteracting osmolytes stabilize mussel gill proteins against thermal denaturation? FIELDS, P.A.*; KOID, A.; JOHN, E.; Franklin and Marshall College; University of Southern California; Franklin and Marshall College peter.fields@fandm.edu
Counteracting osmolytes (CAOs) are small-molecular-weight compounds that stabilize globular proteins in their native state. In a variety of organisms CAOs protect against denaturing stresses including freezing, urea and hydrostatic pressure. In addition, CAOs are known to protect proteins from thermal denaturation in some hyperthermophiles. However, the thermoprotective role of CAOs in eukaryotes has not been described. Using the ribbed mussel Mytilus californianus, we asked whether the composition of CAOs in gill tissue changes after an acute heat shock, and whether extracts of gill osmolytes have thermoprotective properties. We acclimated mussels to 13°C and then exposed them to 26 or 32°C for up to two hours. We used HPLC-MS to determine the composition of the osmolyte pool extracted from homogenized gill tissue. We found that a number of compounds increase significantly in response to heat shock, including m/z 203 (potentially a myo-inositol-Na+ adduct), m/z 126 (taurine), and unidentified compounds at m/z 282 and 496 in positive ion mode. To determine whether gill extracts provide thermoprotection to cytosolic proteins, we incubated a model enzyme, rabbit A4-lactate dehydrogenase, at 45°C in buffer and in increasing concentrations of gill extract, from control and heat-shocked mussels. We hypothesized that increasing extract concentration would extend LDH half-life, but our results suggest this only occurs at lower concentrations (0.25x tissue concentration); at higher concentrations extract has a destabilizing effect. Our preliminary results thus indicate that the composition of osmolytes in M. californianus gill does change in response to heat shock, but it is unclear whether this leads to increased thermoprotection of cytosolic proteins.
