The Plasmodium Class XIV Myosin, MyoB has a Distinct Subcellular Location in Invasive and Motile Stages of the Malaria Parasite, and an Unusual Light Chain [Cell Biology]

March 23rd, 2015 by Yusuf, N. A., Green, J. L., Wall, R. J., Knuepfer, E., Moon, R. W., Schulte-Huxel, C., Stanway, R. R., Martin, S. R., Howell, S. A., Douse, C. H., Cota, E., Tate, E. W., Tewari, R., Holder, A. A.

Myosin B (MyoB) is one of the two short class XIV myosins encoded in the Plasmodium genome. Class XIV myosins are characterised by a catalytic head, a modified neck region and the absence of a tail region. Myosin A (MyoA), the other class XIV myosin in Plasmodium, has been established as a component of the glideosome complex important in motility and cell invasion but MyoB is not well characterised. We analysed the properties of MyoB using three parasite species: P. falciparum, P. berghei and P. knowlesi. MyoB is expressed in all invasive stages (merozoites, ookinetes and sporozoites) of the life cycle and the protein is found in a discrete apical location in these polarised cells. In P. falciparum, MyoB is synthesised very late in schizogony/merogony and its location in merozoites is distinct from, and anterior to, that of a range of known proteins present in the rhoptries, rhoptry neck or micronemes. Unlike MyoA, MyoB is not associated with glideosome complex proteins, including the MyoA light chain, Myosin A tail domain interacting protein (MTIP). A unique MyoB light chain (MLC-B) was identified that contains a calmodulin-like domain at the C-terminus and an extended N-terminal region. MLC-B localises to the same extreme apical pole in the cell as MyoB and the two proteins form a complex. We propose that MLC-B is a MyoB-specific light chain and that for the short class XIV myosins that lack a tail region, the atypical myosin light chains may fulfil that role.
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