Analysis of smooth muscle myosin phosphorylation with native pyrophosphate gels and its application to studies on myosin phosphorylation in contracting smooth muscle

Gizzard smooth muscle myosin, the 20,000 Mr light chain (L20) of which had been phosphorylated in vitro with a calmodulin-myosin light chain kinase system, was separated into 5 isolated bands in a pyrophosphate polyacrylamide gel. Their mobilities were in the following order: myosin with 2 unphosphorylated L20 (GM) less than myosin with 1 unphosphorylated and 1 mono-phosphorylated L20 (GMP1) less than myosin with 2 mono-phosphorylated L20 (GMP2) less than myosin with 1 mono-phosphorylated and 1 di-phosphorylated L20 (GMP3) less than myosin with 2 di-phosphorylated L20 (GMP4). We used this pyrophosphate polyacrylamide gel electrophoresis to analyze the phosphorylated state of taenia coli smooth muscle during K+-induced contraction. During the initial 2 min contraction, phosphorylated forms corresponding to GMP1 and GMP2 were detected in addition to the unphosphorylated form.

Amino acid sequence of the 203-residue fragment of the heavy chain of chicken gizzard myosin containing the SH1-type cysteine residue

A fluorescent fragment of Mr = 23,800 was obtained by the papain digestion of N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylene diamine (abbreviated as IAEDANS)-modified chicken gizzard myosin. The fragment was isolated by gel filtration on a Sephadex G-100 column in the presence of 5 M guanidine-HCl followed by anion exchange chromatography on a QAE Sephadex A-50 column. This fragment contained 203 amino acid residues which could be assigned as a COOH-terminal part of the S-1 heavy chain based on the homology with the known sequence of rabbit skeletal myosin fragment. The amino acid sequence was K-G-M-F-R-T-V- G-Q-L-Y-K-E-Q-L-T-K-L-M-T-T-L-R-N-T-N-P-N-F-V-R-C-I-I-P-N-H-E-K-R-A- G-K-L-D-A-H-L-V-L-E-Q-L-R-C-N-G-V-L-E-G-I-R-I-C-R-Q-G-F-P-N-R-I-V-F-Q- E-F-R-Q-R-Y-E-I-L-A-A-N-A-I-P-K-G-F-M-D-G-K-Q-A-C-I-L-M -I-K-A-L-E-L- D-P-N-L-Y-R-I-G-Q-S-K-I-F-F-R-T-G-V-L-A-H-L-E-E-E-R-D-L-K- I-T-D-V-I-I-A- F-Q-A-Q-C-R-G-Y-L-A-R-K-A-F-A-K-R-Q-Q-Q-L-T-A-M-K-V-I-Q-R-N-C-A -A-Y-L-K-L-R-N-W-Q-W-W-R-L-F-T-K-V-K-P-L-L-Q-V-T-R. The cysteine residue which was modified with IAEDANS was of the SH1 type (Cys-65). Pro-197 was suggested to be the NH2-terminal boundary of the alpha-helical coiled-coil rod sequence of gizzard myosin, based on the homology with the nematode sequence reported by MacLachlan and Karn (Proc. Natl. Acad. Sci. U.S. 80, 4253-4257 (1983)). Three different COOH-terminal peptides (Val-Lys-Pro-Leu-Leu-Gln-Val-Thr-Arg, Val-Lys-Pro-Leu-Leu-Gln, and Val-Lys-Pro-Leu-Leu) were isolated from the tryptic digest of this fragment.(ABSTRACT TRUNCATED AT 400 WORDS)

Structure of the glandular layer and koilin membrane in the gizzard of the adult domestic fowl (Gallus gallus domesticus)

The koilin membrane is formed by the secretions of gland, crypt and surface epithelial cells. Glands form a continuous layer and are arranged in groups of 10-20. They are straight tubes about 500 microns long and 15 microns in diameter and produce rodlets of hard koilin. Hard koilin rodlets (5 microns diameter) form clusters of five or six as they pass through the crypts and enter the koilin membrane. Each rodlet hardens within its gland and maintains its individuality throughout its entire length. Rodlet clusters have previously been called 'rods'. Most of the softer koilin, which fills the spaces between the rodlet clusters, is produced by the surface epithelial cells. These cells form gentle arches between the cavities of adjacent crypts. Horizontal branches between rodlet clusters ('rods') do not exist. There is approximately twice as much surface koilin as rodlet koilin within the membrane. Abrasion of the koilin membrane is not uniform but occurs in a patchy fashion.

Identification by monoclonal antibodies and characterization of human platelet caldesmon

Actin-based gels were prepared from clarified high-salt extracts of human platelets by dialysis against physiological salt buffers. The gel was partially solubilized with 0.3 M KCl. Mice were immunized with the 0.3 M KCl extract of the actin gel, and hybridomas were produced by fusion of spleen cells with myeloma cells. Three hybridomas were generated that secrete antibodies against an 80-kD protein. These monoclonal antibodies stained stress fibers in cultured cells and cross-reacted with proteins in several tissue types, including smooth muscle. The cross-reacting protein in chicken gizzard smooth muscle had an apparent molecular weight of 140,000 and was demonstrated to be caldesmon, a calmodulin and actin-binding protein (Sobue, K., Y. Muramoto, M. Fujita, and S. Kakiuchi, Proc. Natl. Acad. Sci. USA, 78:5652-5655). No proteins of molecular weight greater than 80 kD were detectable in platelets by immunoblotting using the monoclonal antibodies. The 80-kD protein is heat stable and was purified using modifications of the procedure reported by Bretscher for the rapid purification of smooth muscle caldesmon (Bretscher, A., 1985, J. Biol. Chem., 259:12873-12880). The 80-kD protein bound to calmodulin-Sepharose in a Ca++-dependent manner and sedimented with actin filaments, but did not greatly increase the viscosity of F-actin solutions. The actin-binding activity was inhibited by calmodulin in the presence of calcium. Except for the molecular weight difference, the 80-kD platelet protein appears functionally similar to 140-kD smooth muscle caldesmon. We propose that the 80-kD protein is platelet caldesmon.

Heterogeneity of desmin, the muscle-type intermediate filament protein, in blood vessels and astrocytes

Monoclonal antibodies were isolated from mice immunized with chicken gizzard desmin. Antibodies reacting with desmin on immunoblots and selectively decorating chicken and rat intestinal smooth muscle as well as the Z-line in striated muscle, were selected for this study. Based on their staining pattern on cryostat sections of chicken and rat cerebellum, spleen, kidney, aorta and femoral artery, monoclonal supernatants could be divided in three groups: (i) antibodies decorating astrocytes and vascular smooth muscle; (ii) antibodies decorating only vascular smooth muscle; (iii) antibodies decorating only astrocytes. Antibodies in group (i) and (iii) also stained GFA-negative Bergmann glia in chicken cerebellum. It is proposed that desmin may vary depending on the histological localization.

Calcimedins: purification and characterization from chicken gizzard and rat and bovine livers

A procedure for the simultaneous extraction and purification of four calcimedins from chicken gizzard, rat liver, and bovine liver is described. These proteins bind to hydrophobic resins in a calcium-dependent manner similar to calmodulin and troponin C. The four calcimedins purified had molecular weights 67,000 (67K), 35,000 (35K), 33,000 (33K), and 30,000 (30K) as determined by SDS polyacrylamide gel electrophoresis. Their ability to bind calcium was demonstrated using the Hummel-Dreyer method. Their tissue concentration ranged between 1-4 mg/100 g wet weight in the three tissues studied. During gel filtration, calcimedins 67K and 35K, had Rf (Ve-Vo/Vt-Vo) values of 0.46 and 0.74, respectively, indicating monomeric structure. However, the 33K and 30K calcimedins had Rf values of 0.26 (molecular weights greater than 90,000) suggesting that they occur as subunit complexes in their native state. Antibodies raised against the 67K and 35K calcimedins showed cross reactivity suggesting possible common origin. However, peptide mapping studies showed that they are independent proteins with considerable peptide homology. Antibodies to 30/33K calcimedins did not cross-react with either 67K or 35K calcimedins. Moreover, their peptide maps were strikingly different from those of 67K and 35K calcimedins indicating that they are unique. At present, the regulatory function of this group of proteins is not clear. Indirect evidences support the possibility that they are involved in membrane associated events, such as endocytosis and secretion.

Purification and characterization of a protein from chicken gizzard, which inhibits actin polymerization

An actin-polymerization-inhibiting protein, that occurs in crude preparations of vinculin from chicken gizzard, has been purified by DEAE-cellulose and carboxymethyl ion-exchange chromatography. According to sodium dodecyl sulfate (SDS)/polyacrylamide gel electrophoresis and to gel filtration the polymerization-inhibiting protein is heterogeneous and the molecular mass ranges from 20 kDa to 80 kDa. After treatment with acid the polymerization-inhibiting activity was found to migrate on a SDS/polyacrylamide gel as a single band of molecular mass about 32 kDa. The mechanism of the action of the polymerization-inhibiting protein on actin assembly was investigated by the effect on the kinetics of actin polymerization. The polymerization-inhibiting protein blocks elongation of actin filaments at substoichiometric ratios but does not nucleate actin filaments. The equilibrium constant for binding of the polymerization-inhibiting protein to the barbed end of an actin filament was estimated to be 2 X 10(6) M-1 in 100 mM KCl and 2 mM MgCl2, and 35 X 10(6) M-1 in 2 mM MgCl2.

Purification and characterization of a neurite outgrowth factor from chicken gizzard smooth muscle

Chicken gizzard extract contains a macromolecular glycoprotein that promotes neurite outgrowth of dissociated neurons from the ciliary ganglia of chick embryos. Using conventional purification procedures, the factor responsible for the neurite outgrowth (neurite outgrowth factor (NOF)) was purified about 2000-fold to an apparent single protein band (as judged by agarose-polyacrylamide gel electrophoresis). Twenty fmol/cm2 of the purified NOF bound to the culture well was sufficient to exert maximal neuritic response of cultured ciliary ganglia neurons from 8-day-old chick embryos. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that NOF migrated as a single polypeptide of 700 and 210 kDa under nonreducing and reducing conditions, respectively. NOF stained with periodic acid-Schiff reagent and had a sedimentation coefficient of 12 s, a Stokes radius of 114 A, and an isoelectric point of about 5.1. Gizzard NOF was trypsin-sensitive, but resistant to treatment with heparinase, beta-galactosidase, and neuraminidase. Antibody prepared against the purified NOF blocked NOF activity in a dose-dependent manner. The antibody did not inhibit the biological activity of mouse laminin, although it cross-reacted weakly with laminin. Immunohistochemical analysis showed that the antibody against NOF strongly stained the extracellular matrix of cells in thin sections of gizzard, skeletal muscle, heart, liver, and ciliary ganglion, and also the membrane and the cytoplasm of cultured gizzard muscle cells. The present data suggest that gizzard NOF is a novel extracellular matrix glycoprotein which has a role in neurite outgrowth promotion from peripheral neurons in vivo. Although unlikely, the possibility that the NOF is a chick laminin could not be excluded.

Effects of Ca2+ on the conformation and enzymatic activity of smooth muscle myosin

The influence of Ca2+ on the enzymatic and physical properties of smooth muscle myosin was studied. The actin-activated ATPase activity of phosphorylated gizzard myosin and heavy meromyosin is higher in the presence of Ca2+ than in its absence, but this effect is found only at lower MgCl2 concentrations. As the MgCl2 concentration is increased, Ca2+ sensitivity is decreased. The concentration of Ca2+ necessary to activate ATPase activity is higher than that required to saturate calmodulin. The similarity of the pCa dependence of ATPase activity and of Ca2+ binding to myosin and the competition by Mg2+ indicate that these effects involved the Ca2+-Mg2+ binding sites of gizzard myosin. For the actin dependence of ATPase activity of phosphorylated myosin at low concentrations of MgCl2, both Vmax and Ka are influenced by Ca2+. The formation of small polymers by phosphorylated myosin in the presence of Ca2+ could account for the alteration in the affinity for actin. For the actin dependence of phosphorylated heavy meromyosin at low MgCl2 concentrations, Ca2+ induces only an increase in Vmax. To detect alterations in physical properties, two techniques were used: viscosity and limited papain hydrolysis. For dephosphorylated myosin, 6 S or 10 S, Ca2+-dependent effects are not detected using either technique. However, for phosphorylated myosin the decrease in viscosity corresponding to the 6 S to 10 S transition is shifted to lower KCl concentrations by the presence of Ca2+. In addition, a Ca2+ dependence of proteolysis rates is observed with phosphorylated myosin but only at low ionic strength, i.e. under conditions where myosin assumes the folded conformation.

Linear relationship between diphosphorylation of 20 kDa light chain of gizzard myosin and the actin-activated myosin ATPase activity

The addition of large amounts of myosin light chain kinase to the reconstituted gizzard actomyosin shows diphosphorylation of 20 kDa myosin light chain. Accompanying diphosphorylation, the actin-activated myosin ATPase activity was also enhanced. The extent of diphosphorylation and the myosin ATPase activity were clearly demonstrated to be in a linear relationship. From the time course experiment, the conversion of monophosphorylated light chain into one which was diphosphorylated seemed to be a sequential process. Moreover, analyzing phospho-amino acid by using a two-dimensional electrophoresis technique revealed that monophosphorylated light chain contained phosphoserine and diphosphorylated one contained phosphothreonine in addition to phosphoserine.

Conformational studies of myosin phosphorylated by protein kinase C

Smooth muscle myosin from chicken gizzard is phosphorylated by Ca2+-activated phospholipid-dependent protein kinase, protein kinase C, as well as by Ca2+/calmodulin-dependent kinase, myosin light chain kinase (Endo, T., Naka, M., and Hidaka, H. (1982) Biochem. Biophys. Res. Commun. 105, 942-948). We have now demonstrated the effect of phosphorylation by protein kinase C on the smooth muscle myosin molecule. In glycerol/urea polyacrylamide gel electrophoresis the 20,000-dalton light chain phosphorylated by protein kinase C co-migrated with that phosphorylated by myosin light chain kinase. Moreover, the light chain phosphorylated by both kinases migrated more rapidly than did the light chain phosphorylated by either myosin light chain kinase or protein kinase C alone. Myosin phosphorylated by protein kinase C formed a bent 10 S monomer while that phosphorylated by myosin light chain kinase was an unfolded and extended 6 S monomer in the presence of 0.2 M KCl. In addition, myosin phosphorylated by kinases had a sedimentation velocity of 7.3 S, thereby suggesting that the myosin was partially unfolded. The unfolded myosin was visualized electron microscopically. The fraction in the looped form was higher when for myosin phosphorylated by both kinases higher than for that phosphorylated by light chain kinase alone. Therefore, phosphorylation by protein kinase C does not lead to the change in myosin conformation seen with myosin light chain kinase.

Properties of carboxypeptidase A-treated chicken gizzard tropomyosin

Chicken gizzard tropomyosin was digested with carboxypeptidase A at the weight ratios of enzyme to substrate 1:200 and 1:50. Removal of about 16 C-terminal amino acid residues per tropomyosin molecule, at lower enzyme concentration, caused reversion of the effect on skeletal actomyosin ATPase activity from activating to inhibiting without an influence on polymerizability and actin-binding ability. Removal of about 26 C-terminal amino acid residues per molecule, at higher enzyme concentration, resulted in loss of polymerizability and actin binding ability. Digestion of gizzard tropomyosin with carboxypeptidase A has no dramatic effect on its binding to troponin T. The results show that not only the existence of head-to-tail overlapping regions but also their length is important for the functional properties of chicken gizzard tropomyosin.

Amino acid sequence of chicken gizzard gamma-tropomyosin

Chicken gizzard muscle tropomyosin has been fractionated into its two major components, beta and gamma and the amino acid sequence of the gamma component established by the isolation and sequence analysis of fragments derived from cyanogen bromide cleavage and tryptic digestions. Despite its much slower mobility on sodium dodecyl sulfate-polyacrylamide electrophoretic gels, it has the same polypeptide chain length (284 residues) as the alpha and beta components of rabbit skeletal muscle. Evidence for microheterogeneity of the chicken gizzard component was detected both on electrophoretic gels and in the sequence analysis. The gamma component is more closely related to rabbit skeletal alpha-tropomyosin than to the beta component. While the protein is highly homologous to the rabbit skeletal tropomyosins, significant sequence differences are observed in two regions; between residues 42-83 and 258-284. In the latter region (COOH-terminal) the alterations in sequence are very similar to those seen in platelet tropomyosin when compared with the skeletal proteins.

Amino acid sequence of chicken gizzard beta-tropomyosin. Comparison of the chicken gizzard, rabbit skeletal, and equine platelet tropomyosins

Chicken gizzard beta-tropomyosin has the same chain length (284 residues) as other muscle tropomyosins, and is most closely related to the beta component of rabbit skeletal muscle. The majority of the amino acid substitutions are restricted to two regions of the structure, residues 185-216 and 258-284. The altered sequences at the COOH-terminal ends (residue 258-284) of the two gizzard components are very similar to each other and to those in platelet tropomyosin and can be correlated with the reduced affinity of interaction of all three tropomyosins with skeletal troponin T and its T1 fragment. The virtually identical NH2-terminal sequences of all four muscle tropomyosin chains indicates that the gizzard proteins' greater ability to polymerize head-to-tail is due to the sequence changes at its COOH terminus. On the other hand, the weaker head-to-tail aggregation of the platelet protein must be due to its NH2-terminal sequence alterations. Examination of the distribution of amino acids and the frequency of their substitution in the a to g positions of the repeating pseudoheptapeptide for all five tropomyosin sequences (four muscle and one platelet) emphasizes the importance of Glu residues at position e. Examination of those features of the muscle sequences implicated in the stabilization of their coiled-coil structures and in their interactions with F-actin suggest only marginal differences among them, with the possible exception of the chicken gizzard gamma component.

Immunocytochemical localization of 140 kD cell adhesion molecules in cultured chicken fibroblasts, and in chicken smooth muscle and intestinal epithelial tissues

A monoclonal antibody (JG22 MAb) that was previously raised to a chick embryo myogenic cell preparation had been shown to produce rounding and other morphological changes in myogenic cells in culture, and, in some cases, their detachment from the substratum. In other studies it was shown that the epitope recognized by JG22 was associated with a set of 140 kD cell surface glycoproteins. It is shown that this antigen occurs in a wide variety of cell types; in cultured fibroblasts, it is distributed equally between the dorsal and ventral cell surfaces shortly after plating, but appears to become concentrated on the ventral surface as cell spreading proceeds; by immunoelectron microscopic labeling experiments, it is absent from the focal adhesion contact sites formed by fibroblasts with their substrata and with one another, but is present in clusters at the edge of focal adhesions, and within the close contact sites and extracellular matrix contact sites; in smooth muscle cells, it is absent from the membrane-associated dense plaques, but is located in clusters at adjacent membrane sites; in intestinal epithelium, it is present in clusters at the basolateral membranes, but not at the microvilli or within junctional complexes of the brush border of the cell layers. These and other results are consistent with the suggestion that the antigen recognized by JG22 MAb is important cell adhesion molecules, and performs a characteristic function in a variety of cell-cell contacts and cell adhesions.

Crosslinking of actin filaments is caused by caldesmon aggregates, but not by its dimers

A recent report by Bretscher [(1984) J. Biol. Chem. 259, 12873-12880] showed that caldesmon prepared by his method crosslinks actin filaments to form thick bundles. This is in contrast to the results of previous work that caldesmon binds to F-actin but does not cause any gelation [(1981) Proc. Natl. Acad. Sci. USA 78, 5652-5655]. The present work clearly showed that caldesmon purified according to Bretscher does not cause any gelation of F-actin. However, caldesmon aggregates formed by concentration or by freeze-thawing gelated F-actin to form bundles.

Purification of a 175-kDa membrane protein, its localization in smooth and cardiac muscles. Interaction with cytoskeletal protein - vinculin

A new 175-kDa membrane protein was isolated from chicken gizzard smooth muscle. Antibodies to 175-kDa protein were used for localization of this protein in smooth and cardiac muscles. In both types of muscle 175-kDa protein was localized near plasma membrane. 175-kDa protein was able to interact specifically with vinculin immobilized on polysterene surface. It is suggested that this 175-kDa protein may be involved in physical connection between microfilaments and cell membrane.

Effects of various amino acid replacements on the conformational stability of G-actin

Circular dichroic spectra of native, EDTA-treated and heat-denatured G-actin from chicken gizzard smooth muscle are virtually the same as those of rabbit skeletal muscle actin. The rates of changes produced by EDTA or heat in the secondary structure are, however, higher in the case of gizzard actin. Similar differences were found in the rates of inactivation as measured by loss of polymerizability during incubation with EDTA or Dowex 50. The results are explicable in terms of local differences in the conformation at specific site(s) important for maintaining the native state of actin monomer. Involvement of the ATP binding site was shown by measuring the equilibrium constant for the binding of ATP to the two actins. Difference in the conformation of some additional site(s) is indicated by a higher rate constant of inactivation of nucleotide-free actin observed for gizzard actin. No significant difference was found in the equilibrium constant for the binding of Ca2+ at the single high-affinity site in gizzard and skeletal muscle actin. Comparison of inactivation kinetics of actin from chicken gizzard, rabbit skeletal, bovine aorta, and bovine cardiac muscle suggests that the amino acid replacements Val-17----Cys-17 and/or Thr-89----Ser-89 have a destabilizing effect on the native conformation of G-actin. The results indicate that deletion of the acidic residue at position 1 of the amino acid sequence has no effect on the conformation of the ATP binding site and the high-affinity site for divalent cation as well.

Proteolytic substructure of brain myosin

Individual bovine brain myosin molecules visualized by electron microscopy consist of two globular heads and a fibrous tail, like myosin molecules from other sources. Brain myosin, however, showed much lower solubility at moderate to high ionic strength (0.2 to 0.4 M KCl) than gizzard myosin, and the filaments formed at low ionic strength in the presence of Mg2+ were fairly resistant to low concentrations of ATP, by which gizzard myosin filaments were completely solubilized. Brain myosin was digested with low concentrations of papain, alpha-chymotrypsin, or trypsin, and the fragmentation patterns were analyzed by means of polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, sedimentation at low ionic strength, and electron microscopy of the fragments produced. The results indicate that all of the proteases cleave the myosin molecule primarily at sites located in the neck or in the head close to the neck, suggesting that the brain myosin molecule contains a hinge region or an open peptide stretch around these sites. The differences as well as the similarities between the proteolytic fragmentation patterns of brain myosin and other myosins are discussed.

A new simple method of preparing actin from chicken gizzard

A simple method for preparing actin from chicken gizzard was described. This method takes advantage of a property of gizzard tropomyosin, that is, that it does not form Mg paracrystals readily.