α‑actinins of protozoa

February 13, 2020

 

α‑actinins are ubiquitous actin-binding proteins present in most eukaryotes. Due to their ability to bind and cross-link actin filaments in a calcium dependent manner, α‑actinins are important regulators of the intracellular infrastructure.
Although considerably knowledge is available about vertebrate α‑actinins, very little is known about the atypical “short” α‑actinins found in protozoa and fungi. Therefore we have cloned and characterised α‑actinins of Entamoeba and Schizosaccharomyces pombe in order to determine their actin-binding and cross-linking activities as well as calcium-binding properties and structure.
The Entamoeba α‑actinins are of particular interest, as these have been implicated in the adherence and invasion of the human host. Further characterisation of α‑actinins of this parasite will therefore expand the knowledge base and improve the understanding of the mechanism and strategy Entamoeba utilizes for infection. This is important as Entamoeba induced amoebiasis is a major killer in the poorer parts of the world. Since it is likely that other intracellular parasites, such as Trypanosoma, Giardia and Trichomonas, have developed similar mechanisms for infection, such knowledge will be valuable also in these cases.

Spectrin and spectrin-like proteins

February 13, 2020

 

Spectrins are required in fundamental processes that organise membrane compartments in eukaryotic cells. Several isoforms of spectrin exists; some are associated with the plasma membrane whereas others are localized to intracellular compartments, such as ER and Golgi. Apart from a well-established structural role, the functions of these isoforms are far from clear. It is assumed that they provide connections between membrane compartments and the internal cytoskeleton for trafficking and positioning.
Spectrin contains several structural domains, such as SH3, PH and CH motifs as well as several spectrin repeats. These motifs are found in many different proteins, many that are involved in signalling processes.

Together with dystrophin, utrophin and a-actinin, spectrin belongs to a family of preteins with similar properties. The hallmark of this protein family is the presence of three distinct structural domains: an N‑terminal actin-binding domain composed of two calponin homology domains, a central rod domain and a C‑terminal calcium-binding domain. The actin-binding domain, and to a slightly lesser extent, the calcium-binding domain have been conserved during evolution. The rod domain is the most variable part; a‑actinins of vertebrates contain four spectrin repeats whereas dystrophin, for example, contains 30 repeats. In some primitive organisms like protozoa and fungi the rod domain of a‑actinin contains only one or two spectrin repeats. The length of the rod domain is important in the sense that it will determine the density or “packing” of cross-linked actin filaments; a short rod domain will create denser fibers.

  • Research interest

    My research group has a long-standing interest in spectrin and spectrin-like proteins. The major aim is to understand the structural and functional roles of these proteins.
    Presently our efforts are focused on two different areas: to determine the structure and dynamics of a spectrin repeat by NMR and to characterise α-actinin from several different organisms.

  • Contact

    • Phone: +46 (0)90 786 5847
    • Fax: +46 (0)90 786 7655
    • e-mail: lars.backman@chem.umu.se