Meeting Abstract
P1.126 Sunday, Jan. 4 Sequence Comparison of the Calcium-Binding Protein Calsequestrin from Poikilothermic Killifish Species GROVE, T.J.*; SMITH, S.B.; FORT, T.J.; Valdosta State University; Valdosta State University; Valdosta State University tjgrove@valdosta.edu
Isoforms of the sarcoplasmic reticulum (SR) calcium-binding protein calsequestrin (CSQ) are differentially expressed in fast twitch skeletal muscle (CSQ1) and slow twitch skeletal and cardiac muscles (CSQ2). CSQ regulates calcium (Ca2+) release from the SR, enabling muscle contraction and relaxation to occur without a cycle by cycle decline in force development. Upon binding (and releasing) Ca2+, CSQ undergoes dramatic conformational changes. The mechanisms by which this structurally dynamic protein is able to undergo these changes and remain functional under variable physiological temperatures are not known. Killifish are small intertidal fish adapted to the wide variety of thermal environments observed in the coastal waters of North America. Fundulus heteroclitus populations are exposed to different mean annual temperatures along a latitudinal cline (1oper degree latitude) and rapid fluctuations during tidal cycles (up to 15oC in less than an hour). Two congeneric species, F. grandis and F. similis, are found in the warm (22-26oC) coastal waters of eastern Florida and Gulf of Mexico. Partial sequences of putative CSQ have been identified from fast twitch muscle of F. similis and F. heteroclitus and two putative isoforms have been identified from F. grandis, CSQ-A and CSQ-B. Analyses of deduced amino acid sequences indicate that CSQ from F. heteroclitus, F. similis and CSQ-A from F. grandis are highly conserved showing 94-98% identity (98-100% similarity). The putative CSQ-B isoform from F. grandis is less conserved when compared to CSQ from other Fundulus CSQ sequences, showing 58%-64% identity (77-79% similarity). Research is continuing to obtain full length sequences of these putative CSQ isoforms. Supported by NSF IOS-0817805 to TJG and TJF.
