On 2013 Dec 11, Gary Ward commented:

This paper is a classic in the field of parasite cell biology. The stunning electron micrographs provide the first high-resolution look at the substructure of the conoid, a unique cytoskeletal structure found in a variety of apicomplexan parasites. The paper shows that the fibers of the conoid are composed of tubulin, but the protofilament arrangement within the individual fibers is unlike that of any other known tubulin-based structure: rather than a closed tube, the 9 protofilaments are arranged into a “comma” shape. This unique structure may enable the high degree of curvature required of these filaments within the thimble-shaped conoid (diameter 380 nm). FRAP experiments revealed the tubulin subunits are incorporated into the conoid during the early stages of daughter formation, but not in mature parasites. Remarkably, the authors also show that the pitch of the filaments changes as the conoid extends and retracts during parasite motility and host cell invasion.

In the years since this paper was published, additional isoforms of α- and β-tubulin have been discovered for a total of three each (Hu et al. PLOS Pathog [2006] 2(2): e13). It would be interesting to see whether any of these isoforms localize specifically to the conoid or to the other tubulin-based structures within the parasite.

Posted by Gary Ward on behalf of the University of Vermont Toxoplasma Journal Club (UVM ToxoJC); members include Jenna Foderaro, Anne Kelsen, Shruthi Krishnamurthy, Jacqueline Leung, Pramod Rompikuntal, Luke Tilley & Gary Ward

On 2013 Dec 11, Gary Ward commented:

This paper is a classic in the field of parasite cell biology. The stunning electron micrographs provide the first high-resolution look at the substructure of the conoid, a unique cytoskeletal structure found in a variety of apicomplexan parasites. The paper shows that the fibers of the conoid are composed of tubulin, but the protofilament arrangement within the individual fibers is unlike that of any other known tubulin-based structure: rather than a closed tube, the 9 protofilaments are arranged into a “comma” shape. This unique structure may enable the high degree of curvature required of these filaments within the thimble-shaped conoid (diameter 380 nm). FRAP experiments revealed the tubulin subunits are incorporated into the conoid during the early stages of daughter formation, but not in mature parasites. Remarkably, the authors also show that the pitch of the filaments changes as the conoid extends and retracts during parasite motility and host cell invasion.

In the years since this paper was published, additional isoforms of α- and β-tubulin have been discovered for a total of three each (Hu et al. PLOS Pathog [2006] 2(2): e13). It would be interesting to see whether any of these isoforms localize specifically to the conoid or to the other tubulin-based structures within the parasite.

Posted by Gary Ward on behalf of the University of Vermont Toxoplasma Journal Club (UVM ToxoJC); members include Jenna Foderaro, Anne Kelsen, Shruthi Krishnamurthy, Jacqueline Leung, Pramod Rompikuntal, Luke Tilley & Gary Ward