Biochemical and Biological Properties of Myosins

Korn, Edward D.

Abstract

We are interested in the molecular bases of the regulation of the actin-activated ATPase activities of class-I and class-II myosins, the biological roles of these myosins and the regulation of their biological activities. To understand the coupled contributions of myosin heads and tails to enzymatic activity and function, we are studying the properties of chimeras consisting of the motor domain of Dictyostelium myosin II and the tail domains of either Acanthamoeba or smooth muscle myosin II. The chimeras have 10-15 higher actin-activated ATPase activity than wild-type Dictyostelium myosin II but, in contrast to wild-type myosins, this activity is not regulated by phosphorylation of either the regulatory light chain or, in the Acanthamoeba chimera, phosphorylation of the tail. When expressed in myosin II-null cells, both chimeras rescue two essential functions of myosin II - cytokinesis in suspension culture and capping of con A receptors - but do not support full development to fruiting bodies. The structural requirements for localization of myosin II to the cleavage furrow of dividing Dictyostelium cells are under study. We have also deleted the hypertrophoic cardiomyopathy (HCM) surface loop of Dictyostelium myosin II or replaced it by the HCM loop of cardiac or smooth muscle myosin II, by the HCM loop of Acanthamoeba or Aspergillus myosin I, or modified the HCM loop by point mutations including the mutations of human cardiac myosin that cause the genetic disease hypertrophic cardiomyopathy. All of the HCM loop mutants rescue cytokinesis in suspension culture when expressed in Dictyostelium mysoin II-null mutants. None of the mutants appears to support full development, although these studies are not complete. We continue to study the structural basis of the regulation of the actin-activated ATPase activity of Acanthamoeba myosin II by phosphorylation of three sites in the tip of the tail by crystallography of appropriate tail constructs expressed in bacteria and by studying the enzymatic activity and regulation of heavy chain mutants.

Funding Agency

• Agency: National Institute of Health (NIH)
• Institute: National Heart, Lung, and Blood Institute (NHLBI)
• Type: Intramural Research (Z01)
• Project #: 1Z01HL000506-27
• Application #: 6690452
• Study Section: (LCB)
• Support Year: 27
• Fiscal Year: 2002

Institution

• Name: U.S. National Heart Lung and Blood Inst
• 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