SANSCRAINTE, N.D.**; HEFFRON, J.K.*; MOERLAND, T.S.; Florida State University, Tallahassee; Florida State University, Tallahassee; Florida State University, Tallahassee: Molecular size and isoform distribution of parvalbumin from five species of elasmobranchs

Parvalbumin (PV) is a soluble protein of skeletal muscle that facilitates muscular relaxation. While teleost PV has been extensively characterized, little is known about PV in elasmobranchs. Four small coastal shark species were collected by gillnet from several inshore locations in the northern Gulf of Mexico: the Atlantic sharpnose shark (Rhizoprionodon terraenovae), the blacktip shark (Carcharhinus limbatus), the finetooth shark (Carcharhinus isodon) and the bonnethead shark (Sphyrna tiburo). The euryhaline stingray Dasyatis sabina was collected by hook and line from Lake Monroe, part of the St. Johns River system in Florida. A survey of PV size and isoform distribution was performed with SDS-PAGE. PVs were identified by Western blot and amino acid sequencing. All four sharks exhibited a single PV isoform ranging from approximately 12.5 � 13.1 kDa, while the ray D. sabina exhibited two PV isoforms, a major (approximately 13.9 kDa) and a minor (approximately 12.7 kDa). The average molecular weight of PVs from all five elasmobranch species examined is approximately 20% larger than the major PV isoform of Cyprinus carpio, a teleost fish. R. terraenovae N-terminal amino acid sequence (PMTKVLKEDDIN) shares about 90% identity with leopard shark (Triakis semifasciata) N-terminal sequence (PMTKVLKADDINKAI). The N-terminal amino acid sequence for the major PV isoform from D. sabina (PMTKVLKEDDIN) shares no identity with the thornback ray (Raja clavata; phylogenetically a skate) N-terminal sequence (SSKITSILNPADITK), however it shares about 50% identity with T. semifasciata. (Both N. Sanscrainte and J. Heffron contributed equally to this project.)