mAbs specific for calmodulin were used to examine the distribution of calmodulin in vegetative Dictyostelium cells. Indirect immunofluorescence indicated that calmodulin was greatly enriched at the periphery of phase lucent vacuoles. The presence of these vacuoles in newly germinated (non-feeding) as well as growing cells, and the response of the vacuoles to changes in the osmotic environment, identified them as contractile vacuoles, osmoregulatory organelles. No evidence was found for an association of calmodulin with endosomes or lysosomes, nor was calmodulin enriched along cytoskeletal filaments. When membranes from Dictyostelium cells were fractionated on equilibrium sucrose density gradients, calmodulin cofractionated with alkaline phosphatase, a cytochemical marker for contractile vacuole membranes, at a density of 1.156 g/ml. Several high molecular weight calmodulin-binding proteins were enriched in the same region of the gradient. One of the calmodulin-binding polypeptides (molecular mass approximately 150 kD) cross-reacted with an antiserum specific for Acanthamoeba myosin IC. By indirect immunofluorescence, this protein was also enriched on contractile vacuole membranes. These results suggest that a calmodulin-binding unconventional myosin is associated with contractile vacuoles in Dictyostelium; similar proteins in yeast and mammalian cells have been implicated in vesicle movement.
Article|
July 15 1992
Association of calmodulin and an unconventional myosin with the contractile vacuole complex of Dictyostelium discoideum.
Q Zhu,
Q Zhu
Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City 73104.
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M Clarke
M Clarke
Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City 73104.
Search for other works by this author on:
Q Zhu
Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City 73104.
M Clarke
Program in Molecular and Cell Biology, Oklahoma Medical Research Foundation, Oklahoma City 73104.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1992) 118 (2): 347–358.
Citation
Q Zhu, M Clarke; Association of calmodulin and an unconventional myosin with the contractile vacuole complex of Dictyostelium discoideum.. J Cell Biol 15 July 1992; 118 (2): 347–358. doi: https://doi.org/10.1083/jcb.118.2.347
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