Meeting Abstract

P2.14  Friday, Jan. 4  Physiological Role(s) of Arginine Kinase in the Basal Metazoan Sponges REAID, Michael A.*; ELLINGTON, W. R.; Florida State University; Florida State University mreaid@bio.fsu.edu

Phosphagen kinase (PK) reactions are responsible for buffering ATP pools in cells that display high and variable rates of ATP turnover by mitigating spatial and temporal supply and demand imbalances. The two most extensively-studied PKs, arginine kinase (AK) and creatine kinase (CK), are found throughout the metazoan lineage. While sponges lack cell types typically associated with AK and CK expression, our group has shown that both AK and CK are widely distributed in hexactinellid sponges and demosponges. To examine the physiological roles of these enzymes in sponges, tissue from the demosponge Microciona prolifera was dissociated in calcium-magnesium free artificial seawater-EGTA, and cells were separated over a discontinuous Ficoll gradient. Because M. prolifera has been shown to contain no CK activity, each cell fraction was assayed for only AK activity. Each of the four cell fractions exhibited AK activity with the highest being observed in the choanocyte-enriched fraction, the water current-generating cells unique to sponges. It seems likely that AK plays a role in choanocytes by mitigating reaction diffusion constraints between ATP supply by the mitochondria and use in the flagellum. (Supported by NSF grant # IOB-0542236 to WRE)