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Insights into the Dynamics and Actin Interaction of the Intrinsically Disordered Tarp Protein from Chlamydia

Autor: James Tolchard, Ted Hackstadt, Leah Morris, Tharin M. A. Blumenschein, Lawrence A. Eaglen
Rok vydání: 2012
Předmět:
Zdroj: Biophysical Journal. 102(3)
ISSN: 0006-3495
DOI: 10.1016/j.bpj.2011.11.3450
Popis: The human pathogen Chlamydia trachomatis, and all species within the Chlamydiaceae bacterial family, are prokaryotic obligate intracellular parasites. Their host cell internalisation mechanism is well conserved and includes a type-III secreted effector termed Tarp (Translocated actin recruiting protein). Once within the host cell, Tarp is able to nucleate actin filaments and induce a phagocytosis-like Chlamydial encapsulation. While most of Tarp is predicted to be intrinsically disordered, the minimal actin binding sequence from Tarp (100 residues long) contains a short helix which shows homology with the actin binding WH2 motif from WAVE2, maintaining 9 conserved residues across a 15-residue stretch. Using nuclear magnetic resonance (NMR) spectroscopy and the minimal actin binding region, we have determined the residues affected by the Tarp:actin interaction. X-ray structures of other WH2:actin complexes show a short helix binding within the actin hydrophobic cleft and a region of 15-20 extended residues lying along the actin surface. Despite limited sequence homology it is therefore possible that Tarp is binding actin with similar helical and extended elements. Based upon the affected residues of the 100 residue fragment, an 83 residue mutant has been synthesised which still contains the residues affected upon the Tarp:actin interaction. Data from NMR studies of this minimised Tarp fragment shows it is also able to bind G-actin in vitro. Furthermore, NMR spectra of both Tarp fragments alone indicates that in solution they exists as disordered polypeptides. T1 and heteronuclear {1H-15N} NOE relaxation studies of the fragments suggest that a region of decreased dynamics exists which corresponds to the WH2-like helix.
Databáze: OpenAIRE
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