Backbone and side-chain chemical shift assignments for the C-terminal domain of Tcb2, a cytoskeletal calcium-binding protein from Tetrahymena thermophila
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- 作者：Adina M. Kilpatrick ; Theodore E. Gurrola ; Robert C. Sterner…
- 关键词：Tcb2 ; TCBP ; 25 ; Calcium ; binding protein ; Tetrahymena thermophila ; Contractility ; Cytoskeletal
- 刊名：Biomolecular NMR Assignments
- 出版年：2016
- 出版时间：October 2016
- 年：2016
- 卷：10
- 期：2
- 页码：281-285
- 全文大小：1,336 KB
- 刊物类别：Physics and Astronomy
- 刊物主题：None Assigned
- 出版者：Springer Netherlands
- ISSN：1874-270X
- 卷排序：10
文摘
Tcb2 is a putative calcium-binding protein from the membrane-associated cytoskeleton of the ciliated protozoan Tetrahymena thermophila. It has been hypothesized to participate in several calcium-mediated processes in Tetrahymena, including ciliary movement, cell cortex signaling, and pronuclear exchange. Sequence analysis suggests that the protein belongs to the calmodulin family, with N- and C-terminal domains connected by a central linker, and two helix-loop-helix motifs in each domain. However, its calcium-binding properties, structure and precise biological function remain unknown. Interestingly, Tcb2 is a major component of unique contractile fibers isolated from the Tetrahymena cytoskeleton; in these fibers, addition of calcium triggers an ATP-independent type of contraction. Here we report the 1H, 13C and 15N backbone and side-chain chemical shift assignments of the C-terminal domain of the protein (Tcb2-C) in the absence and presence of calcium ions. 1H–15N HSQC spectra show that the domain is well folded both in the absence and presence of calcium, and undergoes a dramatic conformational change upon calcium addition. Secondary structure prediction from chemical shifts reveals an architecture encountered in other calcium-binding proteins, with paired EF-hand motifs connected by a flexible linker. These studies represent a starting point for the determination of the high-resolution solution structure of Tcb2-C at both low and high calcium levels, and, together with additional structural studies on the full-length protein, will help establish the molecular basis of Tcb2 function and unique contractile properties.