Abstract
The genome of the chlorarchiniophyte Bigelowiella natans codes for a protein annotated as an α-actinin-like protein. Analysis of the primary sequence indicate that this protein has the same domain structure as other α-actinins, a N-terminal actin-binding domain and a C-terminal calmodulin-like domain. These two domains are connected by a short rod domain, albeit long enough to form a single spectrin repeat. To analyse the functional properties of this protein, the full-length protein as well as the separate domains were cloned and isolated. Characerisation showed that the protein is capable of cross-linking actin filaments into dense bundles, probably due to dimer formation. Similar to human α-actinin, calcium-binding occurs to the most N-terminal EF-hand motif in the calmodulin-like C-terminal domain. The results indicate that this Bigelowiella protein is a proper α-actinin, with all common characteristics of a typical α-actinin.
Highlights
The cellular cytoskeleton is indispensable for any eukaryotic cell
After subcloning into the expression vector, this plasmid was used as template for preparing constructs of polypeptides used in this report
Direct binding assays as well as transmission electron microscopy showed that the protein cross-links actin filaments into dense bundles
Summary
The cellular cytoskeleton is indispensable for any eukaryotic cell. This protein network, composed to varying degrees of actin filaments, intermediate filaments and microtubules, plays a role in all cellular events. Α-actinin, like other members of the spectrin superfamily, is characterised by three structural domains: a N-terminal actin-binding domain, composed of two calponin homology domains, and a C-terminal calmodulin-like domain (Broderick & Winder, 2005; Wasenius et al, 1987). These domains are connected by a central rod domain consisting of spectrin-like repeats (Blanchard, Ohanian & Critchley, 1989; Otey & Carpen, 2004; Sjöblom, Salmazo & Djinovic-Carugo, 2008). Like Entamoeba histolytica and Encephalitozoon cuniculi have a much shorter rod sequence, that may form a single repeat
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