Paper on MyoB accepted for publication!

Plasmodium falciparum MyoB is a class 14 myosin expressed in all invasive stages of the parasite. MyoB is neither associated with the glideosome nor involved in motility, but during red blood cell invasion, it is found at the apical tip of the parasite and disappears once invasion is completed. Unlike its only known light chain, MLC-B, MyoB is not essential, but MyoB knock-out parasites show a growth defect and are delayed in invasion. In the course of this work, Isa expressed and purified functional MyoB with the help of parasite-specific chaperones. She characterized the binding of MyoB to both actin and MLC-B and determined a low-resolution structure of MyoB-MLC-B in solution using small-angle X-ray scattering. She also found four other putative regulatory light chains that bind to the MyoB IQ2 motif in vitro, but we still do not know of a light chain that would bind to the MyoB essential light chain binding site, IQ1. Isa also determined the kinetics of the MyoB ATPase cycle and found that the ADP release rate from MyoB was faster than the ATP turnover number, and thus, does not appear to be rate-limiting. Given the high affinity to actin and its specific localization, MyoB may have a role in tethering and/or force sensing during early stages of invasion. Our work now calls for further studies on both the role of MyoB and its peculiar light chain MLC-B as well as the biological significance of the additional light chains identified in vitro.

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Pires I, Hung YF, Bergmann U, Molloy JE & Kursula I (2022) Analysis of Plasmodium falciparum myosin B ATPase activity and structure in complex with the calmodulin-like domain of its light chain MLC-B. J Biol Chem in press, preprint available on bioRxiv.