Acanthameba Myosins

Korn, E D.

Abstract

Electric birefringence studies demonstrate differences between filaments of dephosphorylated and phosphorylated myosin II that are interpreted as indicating that filamentous dephosphorylated myosin II is much less flexible around the hinge region. Dephosphorylated monomers and filaments are more rapidly cleaved within the globular head than phosphorylated monomers and filaments. This provides additional evidence for a conformational difference between the dephosphorylated and phosphorylated molecules, even as monomers. This structural difference in monomers is reflected in an in vitro motility assay: phosphorylated monomers are inactive and dephosphorylated monomers fully active. The three myosin I isoforms are differentially localized in the cell: myosin IA is mostly in the actin-rich cortex, myosin IB and IC in the plasma membrane and large vacuole membranes, and only myosin IC in the contractile vacuole membrane. Myosin I heavy chain kinase binds to purified plasma membranes where its autophosphorylation and activity are activated, membrane-bound kinase phosphorylates membrane-bound myosin I and the phosphorylated myosin I has enhanced actin-activated ATPase activity. In vitro, Ca-calmodulin inhibits phospholipid-stimulated autophosphorylation of the kinase and, hence, its activity by competing for the phospholipid binding site. This provides a possible mechanism for Ca regulation of actomyosin I activity in vivo.

Funding Agency

• Agency: National Institute of Health (NIH)
• Institute: National Heart, Lung, and Blood Institute (NHLBI)
• Type: Intramural Research (Z01)
• Project #: 1Z01HL000506-17
• Application #: 3843257
• Support Year: 17
• Fiscal Year: 1992

Institution

• Name: National Heart, Lung, and Blood Institute
• Country: United States

Publications

Baek, Kyuwon; Liu, Xiong; Ferron, Francois et al. (2008) Modulation of actin structure and function by phosphorylation of Tyr-53 and profilin binding. Proc Natl Acad Sci U S A 105:11748-53

Hwang, Kae-Jung; Mahmoodian, Fatemeh; Ferretti, James A et al. (2007) Intramolecular interaction in the tail of Acanthamoeba myosin IC between the SH3 domain and a putative pleckstrin homology domain. Proc Natl Acad Sci U S A 104:784-9

Szczepanowska, Joanna; Korn, Edward D; Brzeska, Hanna (2006) Activation of myosin in HeLa cells causes redistribution of focal adhesions and F-actin from cell center to cell periphery. Cell Motil Cytoskeleton 63:356-74

Liu, Xiong; Shu, Shi; Hong, Myoung-Soon S et al. (2006) Phosphorylation of actin Tyr-53 inhibits filament nucleation and elongation and destabilizes filaments. Proc Natl Acad Sci U S A 103:13694-9

Shu, Shi; Mahadeo, Dana C; Liu, Xiong et al. (2006) S-adenosylhomocysteine hydrolase is localized at the front of chemotaxing cells, suggesting a role for transmethylation during migration. Proc Natl Acad Sci U S A 103:19788-93

Shu, Shi; Liu, Xiong; Korn, Edward D (2005) Blebbistatin and blebbistatin-inactivated myosin II inhibit myosin II-independent processes in Dictyostelium. Proc Natl Acad Sci U S A 102:1472-7

Liu, Xiong; Shu, Shi; Kovacs, Mihaly et al. (2005) Biological, biochemical, and kinetic effects of mutations of the cardiomyopathy loop of Dictyostelium myosin II: importance of ALA400. J Biol Chem 280:26974-83

Ishikawa, Takashi; Cheng, Naiqian; Liu, Xiong et al. (2004) Subdomain organization of the Acanthamoeba myosin IC tail from cryo-electron microscopy. Proc Natl Acad Sci U S A 101:12189-94

Korn, Edward D (2004) The discovery of unconventional myosins: serendipity or luck? J Biol Chem 279:8517-25

Brzeska, Hanna; Szczepanowska, Joanna; Matsumura, Fumio et al. (2004) Rac-induced increase of phosphorylation of myosin regulatory light chain in HeLa cells. Cell Motil Cytoskeleton 58:186-99