RT Journal Article
SR Electronic
T1 Structural role of essential light chains in the apicomplexan glideosome
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 867499
DO 10.1101/867499
A1 Samuel Pazicky
A1 Karthikeyan Dhamotharan
A1 Karol Kaszuba
A1 Haydyn Mertens
A1 Tim Gilberger
A1 Dmitri Svergun
A1 Jan Kosinski
A1 Ulrich Weininger
A1 Christian Löw
YR 2019
UL http://biorxiv.org/content/early/2019/12/06/867499.abstract
AB Apicomplexan parasites, such as Plasmodium falciparum and Toxoplasma gondii, traverse the host tissues and invade the host cells exhibiting a specific type of motility called gliding. The molecular mechanism of gliding lies in the actin-myosin motor localized to the intermembrane space between the plasma membrane and inner membrane complex (IMC) of the parasites. Myosin A (MyoA) is a part of the glideosome, a large multi-protein complex, which is anchored in the outer membrane of the IMC. MyoA is bound to the proximal essential light chain (ELC) and distal myosin light chain (MLC1), which further interact with the glideosome associated proteins GAP40, GAP45 and GAP50. Whereas structures of several individual glideosome components and small dimeric complexes have been solved, structural information concerning the interaction of larger glideosome subunits and their role in glideosome function still remains to be elucidated. Here, we present structures of a T. gondii trimeric glideosome sub complex composed of a myosin A light chain domain with bound MLC1 and TgELC1 or TgELC2. Regardless of the differences between the secondary structure content observed for free P. falciparum PfELC and T. gondii TgELC1 or TgELC2, the proteins interact with a conserved region of TgMyoA to form structurally conserved complexes. Upon interaction, the essential light chains undergo contraction and induce α-helical structure in the myosin A C-terminus, stiffening the myosin lever arm. The complex formation is further stabilized through binding of a single calcium ion to T. gondii ELCs. Our work provides an important step towards the structural understanding of the entire glideosome and uncovering the role of its members in parasite motility and invasion.Author summary Apicomplexans, such as Toxoplasma gondii or the malaria agent Plasmodium falciparum, are small unicellular parasites that cause serious diseases in humans and other animals. These parasites move and infect the host cells by a unique type of motility called gliding. Gliding is empowered by an actin-myosin molecular motor located at the periphery of the parasites. Myosin interacts with additional proteins such as essential light chains to form the glideosome, a large protein assembly that anchors myosin in the inner membrane complex. Unfortunately, our understanding of the glideosome is insufficient because we lack the necessary structural information. Here we describe the first structures of trimeric glideosome sub complexes of T. gondii myosin A bound to two different light chain combinations, which show that T. gondii and P. falciparum form structurally conserved complexes. With an additional calcium-free complex structure, we demonstrate that calcium binding does not change the formation of the complexes, although it provides them with substantial stability. With additional data, we propose that the role of the essential light chains is to enhance myosin performance by inducing secondary structure in the C-terminus of myosin A. Our work represents an important step in unveiling the gliding mechanism of apicomplexan parasites.List of abbreviationsComplex 1trimeric complex of TgELC1, TgMyoA-C and MLC1-S with bound calcium ionComplex 1ftrimeric complex of TgELC1, TgMyoA-C and MLC1-S, calcium-freeComplex 2trimeric complex of TgELC2, TgMyoA-C and MLC1-S with bound calcium ionELCessential light chainGACglideosome associated connectorGAPglideosome associated proteinGAPMglideosome associated protein with multiple membrane spansIMCinner membrane complexMIC1microneme protein 1MLC1myosin light chain 1MLC1-Sshort construct of protein myosin light chain 1, residues 66-210MTIPmyosin A tail interacting proteinMTIP-Sshort construct of protein myosin A tail interacting protein, residues 60-204MyoAmyosin ASAXSsmall angle X-ray scatteringSECsize exclusion chromatographyTgMyoA-CC-terminal construct of T. gondii myosin A, residues