Full-length Plasmodium falciparum myosin A and essential light chain PfELC structures provide new anti-malarial targets

Abstract

Parasites from the genus Plasmodium are the causative agents of malaria. The mobility, infectivity, and ultimately pathogenesis of Plasmodium falciparum rely on a macromolecular complex, called the glideosome. At the core of the glideosome is an essential and divergent Myosin A motor (PfMyoA), a first order drug target against malaria. Here, we present the full-length structure of PfMyoA in two states of its motor cycle. We report novel interactions that are essential for motor priming and the mode of recognition of its two light chains (PfELC and MTIP) by two degenerate IQ motifs. Kinetic and motility assays using PfMyoA variants, along with molecular dynamics, demonstrate how specific priming and atypical sequence adaptations tune the motor’s mechano-chemical properties. Supported by evidence for an essential role of the PfELC in malaria pathogenesis, these structures provide a blueprint for the design of future anti-malarials targeting both the glideosome motor and its regulatory elements.

Actomyosin forces and the energetics of red blood cell invasion by the malaria parasite Plasmodium falciparum

“…Stabilising residues include those between phospho-S19 in the N-terminal extension (NTE, brown) and K764 in the converter (green). PPS structure from [ 21 ]; Rigor-like structure (PDB: 6I7D, neck region and light chain outlines added as schematic, by extension of the last helix of the converter). C Genotyping PCR of PfMyoA-comp and PfMyoA-K764E lines confirmed that the WT p230p locus (green half arrow) is completely lost in PfMyoA-comp, while the integrated locus (IN, grey half arrow) is present.…”

“…Instead, PfMyoA relies on a regulatory light chain or myosin tail interacting protein, MTIP, that binds the extreme end of the neck domain and unusually possesses a long, disordered N-terminal domain to anchor PfMyoA to the IMC [ 19 ]. Maximal in vitro activity of PfMyoA requires the binding of MTIP and a second essential light chain, PfELC [ 20 ], recently shown to stabilise the PfMyoA neck domain and to be critical for parasite replication [ 21 ]. The complex of PfMyoA and its light chains (the PfMyoA triple complex) is anchored to the IMC by a glideosome associated protein, PfGAP45 [ 22 , 23 ] and other GAP proteins embedded in the IMC membranes that together complete the MMC.…”

“…PfMyoA produces directional force by undergoing cycles of ATP hydrolysis and conformational change, allowing it to translocate short, unstable actin filaments [ 26 , 27 ] that are in turn connected to the external substrate. The crystal structures of the PfMyoA motor domain [ 25 ] and triple complex [ 21 ] reveal a unique mechanism of force production involving stabilisation of the rigor-like state by an interaction between K764 in the converter and phospho-S19 in the N-terminal extension (NTE). Disruption of this interaction in vitro reduced the velocity of PfMyoA but increased its maximal force production [ 25 ], suggesting that phosphorylation of S19 is required for maximal myosin velocity.…”

“…PfMyosin B (MyoB) is a second Plasmodium class XIV localised to the extreme merozoite apex, suggesting a function related to invasion, such as organising apical organelles [ 41 ]. Alongside a conditional knockout of light chain PfELC [ 21 ], each mutant was analysed during merozoite invasion by video microscopy revealing three distinct stages of incomplete or aborted RBC invasion depending on actomyosin defect severity. The spectrum of phenotypes seen support the existence of three clear energetic barriers to successful entry, which together with previous works supports a stepwise model for actomyosin force action during merozoite invasion.…”

The Dynamic Roles of the Inner Membrane Complex in the Multiple Stages of the Malaria Parasite

“…GAP45, GAP50, GAP70, and GAPMs (Gaskins et al, 2004;Bullen et al, 2009;Freńal et al, 2010;Yeoman et al, 2011) together with Myosin A (MyoA) (Pinder et al, 1998;Baum et al, 2006;Ridzuan et al, 2012), the myosin A tail-interacting protein [MTIP in Plasmodium spp., or myosin light chain (MLC1) in T. gondii] (Herm- Götz et al, 2002;Bergman et al, 2003) and the "essential light chain 1" protein (ELC1) (Green et al, 2017) have been identified, a comprehensive and systemic identification of all components of the glideosome has not been performed. Recent years have uncovered some structural insights into this protein complex, but this improved understanding is still limited to individual components (Bosch et al, 2006;Bosch et al, 2007;Bosch et al, 2012;Boucher and Bosch, 2014) or to sub-complexes such as the trimeric structure composed of MyoA, ELC1 and MLC1 (Moussaoui et al, 2020;Pazicky et al, 2020) with no structural information on the entire glideosome complex. Another interesting group of proteins are the so called alveolins, an Alveolata specific and conserved multi-protein family encompassing at least 13 proteins ( Table 1) (Gould et al, 2008;Kono et al, 2012;Volkmann et al, 2012;El-Haddad et al, 2013;Tremp et al, 2014;Al-Khattaf et al, 2015).…”