TY - JOUR
T1 - The dictyostelium essential light chain is required for myosin function
AU - Pollenz, Richard S.
AU - Chen, Tung Ling L.
AU - Trivinos-Lagos, Leda
AU - Chisholm, Rex L.
N1 - Funding Information:
We thank Dr. E. Kuzmarski for helpful comments and a generous gift of NU-3 antibody; Dr. J. Bartles for providing [‘251]protein A; Dr. Y. Fukui for many discussions, comments on the manuscript, and gifts of antibodies; Drs. J. Condeelis and D. Knecht for myosin antibodies; and Dr. K. Green for gifts of DAPI and rhodamine palloidin. We also thank an anonymous reviewer for significant scientific and editorial contributions to this paper. This work was supported by NIH grant GM39264 to R. L. C.
PY - 1992/6/12
Y1 - 1992/6/12
N2 - A Dictyostelium mutant (7-11) that expresses less than 0.5% of wild-type levels of the myosin essential light chain (EMLC) has been created by overexpression of antisense RNA. Cells from 7-11 contain wild-type levels of the myosin heavy chain (MHC) and regulatory light chain (RMLC). Myosin isolated from 7-11 cells consists of the MHC with the RMLC associated in reduced stoichiometry, and binds to purified actin in an ATP-sensitive fashion. Purified 7-11 myosin displays calcium-activated ATPase activity with a Vmax about 15%-25% of that of wild type, and a Km for ATP of 27 ± 5 μM versus 83 ± 30 μM for wild type. At actin concentrations as high as 17 μM, 7-11 myosin displays greatly reduced actin-activated ATPase activity. Phenotypically, 7-11 cells resemble MHC mutants, growing poorly in suspension and becoming large and multinucleate. When starved for multicellular development, 7-11 cells take several hours longer than wild-type cells to aggregate. Although multicellular aggregates eventually form, they fail to develop further. The cells are also unable to cap receptors in response to Con A treatment. Since cells expressing the EMLC are phenotypically similar to MHC null mutants, the EMLC appears necessary for myosin function, at least in part because it is required for normal actin-activated ATPase activity.
AB - A Dictyostelium mutant (7-11) that expresses less than 0.5% of wild-type levels of the myosin essential light chain (EMLC) has been created by overexpression of antisense RNA. Cells from 7-11 contain wild-type levels of the myosin heavy chain (MHC) and regulatory light chain (RMLC). Myosin isolated from 7-11 cells consists of the MHC with the RMLC associated in reduced stoichiometry, and binds to purified actin in an ATP-sensitive fashion. Purified 7-11 myosin displays calcium-activated ATPase activity with a Vmax about 15%-25% of that of wild type, and a Km for ATP of 27 ± 5 μM versus 83 ± 30 μM for wild type. At actin concentrations as high as 17 μM, 7-11 myosin displays greatly reduced actin-activated ATPase activity. Phenotypically, 7-11 cells resemble MHC mutants, growing poorly in suspension and becoming large and multinucleate. When starved for multicellular development, 7-11 cells take several hours longer than wild-type cells to aggregate. Although multicellular aggregates eventually form, they fail to develop further. The cells are also unable to cap receptors in response to Con A treatment. Since cells expressing the EMLC are phenotypically similar to MHC null mutants, the EMLC appears necessary for myosin function, at least in part because it is required for normal actin-activated ATPase activity.
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U2 - 10.1016/0092-8674(92)90614-I
DO - 10.1016/0092-8674(92)90614-I
M3 - Article
C2 - 1535025
AN - SCOPUS:0026776330
SN - 0092-8674
VL - 69
SP - 951
EP - 962
JO - Cell
JF - Cell
IS - 6
ER -