scholarly journals Calcium-calmodulin and regulation of brush border myosin-I MgATPase and mechanochemistry

1993 ◽  
Vol 122 (3) ◽  
pp. 613-621 ◽  
Author(s):  
JS Wolenski ◽  
SM Hayden ◽  
P Forscher ◽  
MS Mooseker
Keyword(s):  
Heavy Chain ◽  
Brush Border ◽  
Light Chains ◽  
Binding Domains ◽  
Myosin I ◽  
Acidic Phospholipids ◽  
Mgatpase Activity

We examined the Ca(2+)-dependent regulation of brush border (BB) myosin-I by probing the possible roles of the calmodulin (CM) light chains. BB myosin-I MgATPase activity, sensitivity to chymotryptic digestion, and mechanochemical properties were assessed using 1-10 microM Ca2+ and in the presence of exogenously added CM since it has been proposed that this myosin is regulated by calcium-induced CM dissociation from the 119-kD heavy chain. Each of these BB myosin-I properties were dramatically altered by the same threshold of 2-3 microM Ca2+. Enzymatically active NH2-terminal proteolytic fragments of BB myosin-I which lack the CM binding domains (the 78-kD peptide) differ from CM-containing peptides in that the former is completely insensitive to Ca2+. Furthermore, the 78-kD peptide exhibits high levels of MgATPase activity which are comparable to that observed for BB myosin-I in the presence of Ca2+. This suggests that Ca2+ regulates BB myosin-I MgATPase by binding directly to the CM light chains, and that CM acts to repress endogenous MgATPase activity. Ca(2+)-induced CM dissociation from BB myosin-I can be prevented by the addition of exogenous CM. Under these conditions Ca2+ causes a reversible slowing of motility. In contrast, in the absence of exogenous CM, motility is stopped by Ca2+. We demonstrate this reversible slowing is not due to the presence of inactive BB myosin-I molecules exerting a "braking" effect on motile filaments. However, we did observe Ca(2+)-independent slowing of motility by acidic phospholipids, suggesting that factors other than Ca2+ and CM content can affect the mechanochemical properties of BB myosin-I.

Characterization of the enterocyte-like brush border cytoskeleton of the C2BBe clones of the human intestinal cell line, Caco-2

1992 ◽  
Vol 102 (3) ◽  
pp. 581-600 ◽  
Author(s):  
M.D. Peterson ◽  
M.S. Mooseker
Keyword(s):  
Molecular Mass ◽  
Cell Line ◽  
Heavy Chain ◽  
Brush Border ◽  
Laser Scanning ◽  
Human Colon ◽  
Cell Types ◽  
Intestinal Cell ◽  
Myosin I

The brush border (BB) of the enterocyte is a well-studied example of the actin-based cytoskeleton. We describe here a cell culture model that expresses a faithful representation of the in vivo structure. Two clones (C2BBe 1 and 2) isolated from the cell line Caco-2 (derived from a human colonic adenocarcinoma) formed a polarized monolayer with an apical BB morphologically comparable to that of the human colon. BBs could be isolated by standard methods and contained the microvillar proteins villin, fimbrin, sucrase-isomaltase and BB myosin I, and the terminal web proteins fodrin and myosin II. The immunolocalization of these proteins in confluent, filter-grown monolayers was determined by laser scanning confocal microscopy; patterns of distribution comparable to those in human enterocytes were observed. Sedimentation analysis of cell homogenates derived from C2BBe cells and human colonic epithelial cells demonstrated similar patterns of fractionation of BB proteins; the physical association of those proteins, as determined by extraction from the BB, was also comparable between the two cell types. Like enterocytes of the human intestine, C2BBe cells expressed multiple myosin I immunogens reactive with a head domain-specific monoclonal antibody raised against avian BB myosin I, one of which co-migrated with the approximately 110 kilodalton (kDa) heavy chain of human BB myosin I. In addition, the C2BBe cells express a pair of higher molecular mass immunogens (130 and 140 kDa). These myosin I immunogens all exhibit ATP-dependent association with the C2BBe cytoskeleton. Although the higher molecular mass immunogens were detected in several other human intestinal lines examined, including the parent Caco-2 line, none of these other lines expressed detectable levels of the 110 kDa immunogen, which is presumed to be the heavy chain of human BB myosin I.

scholarly journals Partial deduced sequence of the 110-kD-calmodulin complex of the avian intestinal microvillus shows that this mechanoenzyme is a member of the myosin I family.

1989 ◽  
Vol 109 (6) ◽  
pp. 2895-2903 ◽  
Author(s):  
A Garcia ◽  
E Coudrier ◽  
J Carboni ◽  
J Anderson ◽  
J Vandekerkhove ◽  
...  
Keyword(s):  
Fusion Protein ◽  
Heavy Chain ◽  
Brush Border ◽  
Amino Terminal ◽  
Terminal Domain ◽  
Carboxy Terminal Domain ◽  
Head Domain ◽  
Myosin I ◽  
Chicken Tissue ◽  
Carboxy Terminal

The actin bundle within each microvillus of the intestinal brush border is laterally tethered to the membrane by bridges composed of the protein complex, 110-kD-calmodulin. Previous studies have shown that avian 110-kD-calmodulin shares many properties with myosins including mechanochemical activity. In the present study, a cDNA molecule encoding 1,000 amino acids of the 110-kD protein has been sequenced, providing direct evidence that this protein is a vertebrate homologue of the tail-less, single-headed myosin I first described in amoeboid cells. The primary structure of the 110-kD protein (or brush border myosin I heavy chain) consists of two domains, an amino-terminal "head" domain and a 35-kD carboxy-terminal "tail" domain. The head domain is homologous to the S1 domain of other known myosins, with highest homology observed between that of Acanthamoeba myosin IB and the S1 domain of the protein encoded by bovine myosin I heavy chain gene (MIHC; Hoshimaru, M., and S. Nakanishi. 1987. J. Biol. Chem. 262:14625-14632). The carboxy-terminal domain shows no significant homology with any other known myosins except that of the bovine MIHC. This demonstrates that the bovine MIHC gene most probably encodes the heavy chain of bovine brush border myosin I (BBMI). A bacterially expressed fusion protein encoded by the brush border 110-kD cDNA binds calmodulin. Proteolytic removal of the carboxy-terminal domain of the fusion protein results in loss of calmodulin binding activity, a result consistent with previous studies on the domain structure of the 110-kD protein. No hydrophobic sequence is present in the molecule indicating that chicken BBMI heavy chain is probably not an integral membrane protein. Northern blot analysis of various chicken tissue indicates that BBMI heavy chain is preferentially expressed in the intestine.

Recombinant expression of the brush border myosin I heavy chain

1995 ◽  
Vol 32 (2) ◽  
pp. 151-161 ◽  
Author(s):  
Kathleen Collins ◽  
Paul T. Matsudaira
Keyword(s):  
Heavy Chain ◽  
Brush Border ◽  
Recombinant Expression ◽  
Myosin I

scholarly journals Immunolocalization of myosin I heavy chain kinase in Acanthamoeba castellanii and binding of purified kinase to isolated plasma membranes.

1991 ◽  
Vol 115 (1) ◽  
pp. 109-119 ◽  
Author(s):  
D Kulesza-Lipka ◽  
I C Baines ◽  
H Brzeska ◽  
E D Korn
Keyword(s):  
Plasma Membrane ◽  
Heavy Chain ◽  
Plasma Membranes ◽  
Acanthamoeba Castellanii ◽  
Permeabilized Cells ◽  
Electrophoretic Mobilities ◽  
Myosin I ◽  
Substrate Level ◽  
Membrane Bound ◽  
Acidic Phospholipids

The actin-activated Mg(2+)-ATPase activities of Acanthamoeba myosins I are known to be maximally expressed only when a single threonine (myosin IA) or serine (myosins IB and IC) is phosphorylated by myosin I heavy chain kinase. The purified kinase is highly activated by autophosphorylation and the rate of autophosphorylation is greatly enhanced by the presence of acidic phospholipids. In this paper, we show by immunofluorescence and immunoelectron microscopy of permeabilized cells that myosin I heavy chain kinase is highly concentrated, but not exclusively, at the plasma membrane. Judged by their electrophoretic mobilities, kinase associated with purified plasma membranes may differ from the cytoplasmic kinase, possibly in the extent of its phosphorylation. Purified kinase binds to highly purified plasma membranes with an apparent KD of approximately 17 nM and a capacity of approximately 0.8 nmol/mg of plasma membrane protein, values that are similar to the affinity and capacity of plasma membranes for myosins I. Binding of kinase to membranes is inhibited by elevated ionic strength and by extensive autophosphorylation but not by substrate-level concentrations of ATP. Membrane-bound kinase autophosphorylates to a lesser extent than free kinase and does not dissociate from the membranes after autophosphorylation. The co-localization of myosin I heavy chain kinase and myosin I at the plasma membrane is of interest in relation to the possible functions of myosin I especially as phospholipids increase kinase activity.

Immunochemical Evidence That Myosin I Heavy Chain-Like Protein Is Identical to the 110-Kilodalton Brush-Border Protein1

1989 ◽  
Vol 106 (3) ◽  
pp. 455-459 ◽  
Author(s):  
Minoru Hoshimaru ◽  
Yasushi Fujio ◽  
Kenji Sobue ◽  
Tetsuo Sugimoto ◽  
Shigetada Nakanishi
Keyword(s):  
Heavy Chain ◽  
Brush Border ◽  
Myosin I

scholarly journals Monoclonal antibodies demonstrate limited structural homology between myosin isozymes from Acanthamoeba.

1984 ◽  
Vol 99 (3) ◽  
pp. 1002-1014 ◽  
Author(s):  
D P Kiehart ◽  
D A Kaiser ◽  
T D Pollard
Keyword(s):  
Monoclonal Antibodies ◽  
Heavy Chain ◽  
Solid Phase ◽  
Polyclonal Antibodies ◽  
Myosin Ii ◽  
Light Chains ◽  
Homologous Region ◽  
Myosin Isozymes ◽  
Antibody Staining ◽  
Myosin I

We used a library of 31 monoclonal and six polyclonal antibodies to compare the structures of the two classes of cytoplasmic myosin isozymes isolated from Acanthamoeba: myosin-I, a 150,000-mol-wt, globular molecule; and myosin-II, a 400,000-mol-wt molecule with two heads and a 90-nm tail. This analysis confirms that myosin-I and -II are unique gene products and provides the first evidence that these isozymes have at least one structurally homologous region functionally important for myosin's role in contractility. Characterization of the 23 myosin-II monoclonal antibody binding sites by antibody staining of one-dimensional peptide maps and solid phase, competitive binding assays demonstrate that they bind to at least 15 unique sites on the myosin-II heavy chain. The antibodies can be grouped into six families, whose members bind close to one another. None of the monoclonal antibodies bind to myosin-II light chains and polyclonal antibodies against myosin-II light or heavy chain bind only to myosin-II light or heavy chains, respectively: no antibody binds both heavy and light chains. Six of eight monoclonal antibodies and one of two polyclonal sera that react with the myosin-I heavy chain also bind to determinants on the myosin-II heavy chain. The cross-reactive monoclonal antibodies bind to the region of myosin-II recognized by the largest family of myosin-II monoclonal antibodies. In the two papers that immediately follow, we show that this family of monoclonal antibodies to myosin-II binds to the myosin-II tail near the junction with the heads and inhibits both the actin-activated ATPase of myosin-II and contraction of gelled cytoplasmic extracts of Acanthamoeba cytoplasm. Further, this structurally homologous region may play a key role in energy transduction by cytoplasmic myosins.

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