Mutant/mutation
The mutant expresses a C-terminal GFP-tagged version of myosin B

Protein (function)
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.
The malaria parasite genome contains six genes that encode myosins. Two of these genes code for short class XIV myosins, which are restricted to Apicomplexan parasites and other members of the Alveolata. These myosins differ from most others in that, while they have the highly conserved 'head' region that binds actin and hydrolyses ATP, and the 'neck' region that acts as the lever arm and contains IQ-motifs to which myosin light chains bind, they have no 'tail' region. The tail normally allows oligomerisation, cargo binding and determines the subcellular location of the myosin.

Phenotype
Expression of MyoBGFP in the invasivie stages (merozoites, ookinetes sporozoites). MyoB-GFP was detected as a distinct single dot  with the fluorescence concentrated at the extreme apical end of the cell. In salivary gland sporozoites, in addition to the bright apical spot of fluorescence,  a more diffuse fluorescence within the body of the parasite was also observed. This was not observed in any other stage.


Additional information
Through analysis of MyoB in P. falciparum, P. knowlesi and P. berghei evidence is presented that 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 Nterminal region. MLC-B localises to the same extreme apical pole in the cell as MyoB and the two proteins form a complex.

Other mutants