Search by key word or author


 
Contributed Papers: Oral Presentations
Cell Biology

Identification and function of the EtMIC4-EtMIC5 protein complex. A novel microneme complex of Eimeria tenella

Javier Periz, Andrew Gill, Lawrence Hunt and Fiona Tomley
Institute for Animal Health, Compton


Eimeria tenella, like other members of the Apicomplexa, shares a conserved mechanism of motility and invasion which relies on the sequential exocytosis of adhesive proteins from secretory organelles such as micronemes. We have investigated the function of EtMIC4, a 240 kDa transmembrane microneme protein of Eimeria tenella that displays a striking multimodular organisation. EtMIC4 contains 16 TSP-1 like domains and 31 EGF-like domains, both of which are found in other soluble and cell surface eukaryotic proteins that mediate protein interactions.. Using non-denaturating anion exchange chromatography and size exclusion chromatography, we identified the presence of a high molecular weight protein complex formed between EtMIC4 and EtMIC5, another microneme protein which contains 11 Apple domains. Cell blot assays showed that EtMIC5 is responsible for binding the complex to cell lines. We have also used recombinant polypeptides expressed in E. coli to investigate structural properties of the calcium binding EGF-like domains in EtMIC4. Circular dichroism analysis and mass spectrometry we show that, in the presence of calcium, these EGFs mediate resistance to proteolytic degradation and suggest that this confers on the molecule an elongated shape. This suggests a potential role for the calcium binding EGF repeats in EtMIC4 in forming an extended stalk region within the molecule

 

back  |  print