Occurrence of Articulins and Epiplasmins in Protists¹

Abstract

The cortex of ciliates. dinoflagellates, and euglenoids comprises a unique structure called the epiplasm, implicated in pattern-forming processes of the cell cortex and in maintaining cell shape. Articulins, a novel class of cytoskeletal proteins, are major constituents of the epiplasm in the flagellate Euglena gracilis and the ciliate Pseudomicrothorax dubius. The hallmark of articulins is a core domain of repetitive motifs of alternating valine and proline residues, the VPV-motif. The VPV-motif repeats are 12 residues long. Positively and negatively charged residues segregate in register with valine and proline positions. The VPV-motif is unique to articulins. The terminal domains flanking the core are generally hydrophobic and contain a series of hexa- or heptapeptide repeats rich in glycine and hydrophobic residues. Using molecular and immunological tools we show that articulins are also present in the dinoflagellate Amphidinium carterae and the ciliates Paramecium tetraurelia and Paramecium caudatum, Tetrahymena pyriformis, and Euplotes aediculatus. Our analysis further shows that epiplasmins, a group of epiplasmic proteins first characterized in Paramecium, are also present in all these species. Moreover, we present evidence that epiplasmins and articulins represent two distinct classes of cytoskeletal proteins.

Visualization of the funis of Giardia lamblia by high-resolution field emission scanning electron microscopy—new insights

“…After the emergence of the posteriorlateral flagella the funis microtubules are seen anchored to the underlying material in the plasma membrane. Many protists posses a unique cortical cytoplasm: the epiplasm, which is a prominent proteinaceous layer underlying the plasma membrane (Huttenlauch and Stick, 2003). Thus, the funis microtubules seem to be anchored to the epiplasm in the most posterior region of Giardia.…”

Evolution of phototaxis

“…Plants evolved a cell wall, alveolates evolved cortical alveoli (possibly already in the plant-chromalveolate common ancestor) and subpellicular microtubules (Gould et al 2008). Excavates evolved rigidifying pellicle strips, composed of articulins (Huttenlauch & Stick 2003), which run underneath the plasma membrane from anterior to posterior (Leander & Farmer 2000). Fungi evolved chitin cell walls, and animals evolved multi-cellular tissues that are held together by cell adhesion and organized by developmental signalling and planar polarity.…”

A Novel Actin-Related Protein Is Associated with Daughter Cell Formation in Toxoplasma gondii

“…The IMC is made up of flattened vesicles that overlay a basket weave of filamentous proteins called the subpellicular network (29). The function of these proteins is poorly understood, but they are similar to articulins, specialized cytoskeletal components found in other protozoa such as the ciliates and the euglenids (19). To date, only three IMC proteins have been experimentally characterized in Toxoplasma (14,15,25,26), although the genome indicates that a much larger family of these proteins is present (www.ToxoDB.org) (23).…”