Functional Characterization of Calsequestrin from the Killifish Fundulus heteroclitus
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Authors
Nienow, Tatyana Ekaterina
Issue Date
2012-05-04
Type
Thesis
Language
Keywords
Calsequestrin , Killfish , FCSQ1 , Calcium , CSQ , adaptation
Alternative Title
Abstract
Calsequestrin (CSQ) is the main calcium-binding protein that regulates calcium
release from the sarcoplasmic reticulum in both skeletal and cardiac muscles. CSQ
undergoes dramatic conformational changes upon binding and releasing calcium. While the properties of CSQ have been well studied in homeotherms, less work has been done in poikilothermic organisms. In this study skeletal muscle CSQ from the killifish
Fundulus heteroclitus (FCSQ1) was sequenced, expressed, and characterized. The
calculated molecular weight of FCSQ1, excluding its signal sequence, is approximately
49 kDa. The primary structure of FCSQ1 is highly conserved when compared to CSQs
from other vertebrates, although its overall sequence similarity, theoretical pI (3.94), and
tail length, are more similar to the cardiac isoform rather than the skeletal muscle
isoform. At 15°C, pH 7.5, the KD of FCSQ1 is 0.10 ± 0.006 mM in the absence of KCl
and 0.14 ± 0.018 mM in the presence of 0.1 M KCl as calculated from a fluorescence
spectroscopy-based assay. This is lower than the generally reported KD of 1 mM, but is
similar to the results obtained using a similar technique by Hidalgo et al. (1996). FCSQ1
also exhibits pH independence and moderate temperature dependence, suggesting that
there is partial adaptation to the varying thermal environment in which F. heteroclitus is
found.
Description
Citation
Publisher
Valdosta State University
License
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