Detection of antibodies specific to sodium dodecyl sulfate-treated proteins

An auxin-induced polypeptide in dicotyledonous plants

Antisera were raised to a 70-kD (kilodalton) soybean (Glycine max) protein encoded by a 2,4-dichlorophenoxyacetic acid (2,4-D) inducible mRNA, GH3. These antisera have been used to probe protein blots to study the kinetics and specificity of the GH3 induction response as well as the species specificity and intracellular location of the protein. Detectable levels of the GH3 protein are induced by 2,4-D within 2 h in elongating hypocotyl sections, root sections, and etiolated plumules, and within 30-60 min in soybean suspension cells. Synthesis of the GH3 protein is induced by a variety of auxins. Other plant hormones such as gibberellic acid, cytokinin and ethylene added with or whithout 2,4-D do not alter the level of GH3 protein induction. The GH3 protein is found only in the S100 fraction and is not associated with the nucleus or cell wall. This antiserum also reacts with a 2,4-D-inducible 70-kD protein in other dicots.

Electrophoretic and immunological study of myosin light chains from freshwater teleost fishes

White muscle myosin light chains from nine freshwater teleosts show a qualitative and quantitative variability on PAGE without phylogenetic correlation. They look different from their higher vertebrate counterparts mainly with regard to electric charge and relative amounts of alkali light chains corresponding to various contents of isoenzymic forms of white muscle myosin. Antibodies against carp white myosin LC1 recognize almost entirely white muscle LC1 from the other fishes and to a lesser degree LC1 from other muscles and vertebrates. The primary structure of this light chain is thus relatively constant. LC2 from carp cardiac muscle and mammalian slow and cardiac muscle do not react at all.

Generation, characterization and ELISA of monospecific antibodies against the subunits of a Ca2+-dependent protein kinase and a Ca2+-transport ATPase from rabbit skeletal muscle

Monospecific precipitating sheep antibodies were generated for the first time against the purified, homogeneous alpha-, beta- and gamma-subunits of the Ca2+-dependent protein kinase, phosphorylase kinase, from rabbit muscle. As reference, antibodies against the holoenzyme and the CA2+-transport ATPase of sarcoplasmic reticulum were induced. In all cases antibody titers could be quantitated (standard error 5-10%) by enzyme-linked immunosorbent assay. Differentiation of antibody binding was achieved by quantitative precipitation and complement fixation assays. In general maximal antibody titers were reached 56 days after primary immunization and high titers (approximately 5000) were maintained for several weeks. Anti-alpha, anti-beta and anti-gamma avidly precipitate the denatured subunits employed as immunogens as well as the native enzyme. No cross-reactivity between antibodies against a specific subunit and any of the other heterologous subunits was demonstrable in double immunodiffusion assays providing no evidence for immunologically identical sites on the alpha-, beta- and gamma-subunits. Since anti-alpha, anti-beta and anti-gamma strongly inhibit enzyme activity, it is likely that they do so primarily by sterically interfering with the binding of the large substrate phosphorylase b (Mr 2.0 X 10(5)) to phosphorylase kinase (Mr 1.3 X 10(6)). It cannot be excluded, however, that anti-beta and anti-gamma bind to the active sites on these 2 subunits.

Comparison of the tryptic digestion pattern of subfragments 1 from V1 and V3 rat cardiac isomyosins

The limited tryptic digestion patterns of the chymotryptic subfragment 1 (S1) of the two rat ventricular isomyosins V1 and V3, were compared under several conditions. Pure S1V1 was obtained from 3-week-old rats and pure S1V3 from adult rats 6 weeks after hypophysectomy. To localize the sites of trypsin susceptibility and to determine the distribution of the peptides along the S1 molecule, we used, as a probe, antibodies raised against a pig cardiac 29-kDa peptide. We demonstrate that this peptide contains the N-acetyl group located on the N-terminal part of the cardiac myosin molecule. In S1V1 we observed two major sites of proteolysis, independently of the digestion conditions: they are located at 27kDa and 80kDa from the N terminus as in skeletal muscle S1.S1V3 appears much more sensitive to the proteolysis conditions: at least two additional sites of cleavage are present in the 50-kDa peptide when digested at pH 8.0. Decrease in the pH from 8.0 to 7.0 or the presence of Mg-ATP have no effect on the digestion of S1V1 while these ambient factors protect the 50-kDa peptide of S1V3 from breakdown. We conclude that the 50-kDa peptide is a variable portion of the myosin molecule, the conformation of which is sensitive to ambient factors such as the pH or the presence of nucleotides.

Studies on the antigenic sites of actin: a comparative study of the immunogenic crossreactivity of invertebrate actins

The structural homologies of invertebrate actins with cytoplasmic vertebrate actins have recently been substantiated by comparative sequence analyses. This suggests that cytoplasmic actin is the ancestral precursor of smooth and striated muscle actin in vertebrates. We have raised antibodies in rabbits against a number of invertebrate muscle actins and have characterized the antisera by means of the highly sensitive ELISA method, which allows quantitation of nanomolar amounts of actin. Despite the fact that the invertebrate actins examined are very similar in primary structure, our results indicate that antibodies raised against them clearly distinguish between only a few amino-acid substitutions, and that the immunoreactivities quantitatively reflect the genetic divergence of this ubiquitous conservative protein. Examination of several proteolytic fragments of scallop actin for immunoreactivity with the homologous antiserum suggests that the major antigenic sites of actin are located within the amino terminal region of the molecule, while a carboxy terminal fragment comprising residues 69-372 exhibits very weak crossreactivity. Immunoadsorption experiments further indicate that species-specific antibodies are directed to antigenic determinants in the N-terminal region. This finding is supported by an examination of the effects of chemical modifications to Tyr, His, Arg, and Cys residues on the immunoreactivity of actin. Interaction with DNAase I markedly decreases the immunoreactivity of actin. This is consonant with the finding that the amino terminal peptide comprising residues 1-207 inhibits DNAase I, whilst a tryptic fragment fails to bind to the enzyme. The interaction is abolished by EDTA and the removal of the tightly bound cation is accompanied by a conformational change, shown by shifts in circular dichroic spectra. The possible involvement of the amino terminal peptide of actin in cation binding is discussed.

Immunochemical analysis of myosin heavy chain during avian myogenesis in vivo and in vitro

Monoclonal antibodies (McAbs) against the myosin heavy chain (MHC) of adult chicken pectoralis muscle have been tested for reactivity with pectoralis myosin at selected stages of chick development in vivo and in vitro. Three such McAbs, MF 20 and MF 14, which bind to light meromyosin, and MF 30, which binds to myosin subfragment two (S2), were used to assay the appearance and accumulation of specific MHC epitopes with: (a) indirect, solid phase radioimmune assay (RIA), (b) immunoautoradiography, (c) immunofluorescence microscopy. McAb MF 20 bound strongly and equivalently to MHC at all stages of embryonic development in vivo. In contrast, the MF 30 epitope was barely detectable at 12 d of incubation but its concentration rose rapidly just before hatching. No detectable binding of MF 14 to pectoralis myosin could be measured during myogenesis in vivo until 1 wk after hatching. Immunofluorescence studies revealed that all three epitopes accumulate in the same myocytes of the developing pectoralis muscle. Since all three McAbs bound with high activity to native and denatured forms of myosin, it is unlikely that differential antibody reactivity can be explained by conformational changes in myosin during development in vivo. When myogenesis in vitro was monitored using the same McAbs, MF 20 bound to the MHC at all stages tested while reactivity of MF 30 and MF 14 with myosin from cultured muscle was never observed. Thus, this study demonstrates three different immunochemical states of the MHC during development in vivo of chick pectoralis muscle and the absence of later occurring immunochemical transitions in the MHC of cultured embryonic muscle.

Denervation of newborn rat muscle does not block the appearance of adult fast myosin heavy chain

Several observations, both in vivo and in vitro, have indicated that the development and maturation of mammalian skeletal muscle fibres is influenced by nerve-muscle interactions. Morphological maturation of newly regenerated adult mouse muscle fibers in an organotypic nerve-muscle culture system depends on the presence of spinal cord neurones. Sciatic nerve transection in newborn rats has been shown to modify the development of the histochemical and contractile properties of the denervated muscles. In addition, neural influences are important for the appearance of certain of the myosin small subunits. It has been proposed that the nerve also controls the changes in myosin heavy chain isozymes appearing during development. One such transition occurs in rat muscle where the neonatal form of myosin heavy chain is replaced by the adult form during the second post-natal week. Here we demonstrate that innervation of the rat gastrocnemius muscle (a fast-contracting muscle in the adult) is not required for the appearance of the adult form of myosin heavy chain.

Use of antibodies against dodecylsulfate-denatured heavy meromyosins to probe structural differences between muscular myosin isoenzymes

Heavy meromyosin, a tryptic myosin fragment, was purified from rabbit fast twitch muscles and rat cardiac ventricles. Both types of heavy meromyosin were denatured by sodium dodecylsulfate and used to immunize guinea-pigs after chromatography on Sephadex G-10 to remove excess dodecylsulfate. Micro-complement fixation analysis showed that the antisera were specific to a denatured configuration of heavy meromyosin and myosin, and hardly recognized the native proteins. Cross-reactions performed with both rabbit skeletal and rat cardiac antisera indicated that the antigenic structures of denatured myosins varied according both to species (man, rabbit, rat or mouse), and to muscle-type (red skeletal slow twitch, while skeletal fast twitch, cardiac atria or cardiac ventricles). Denatured heavy meromyosin chromatography on Sephadex G-200 in the presence of 0.1% sodium dodecylsulfate enabled separation of several polypeptides groups. Of these, a polypeptide of Mr 29000 was the most reactive and exhibited the same immunological specificities as the whole myosin molecule. The use of antibodies against denatured heavy meromyosin in conjunction with micro-complement fixation therefore provides a discriminant means, not only for estimating the structural relationship between several myosin isoenzymes, but also for localizing constant and variable regions in the heavy chains of these isoenzymes.

Myosin isoenzyme redistribution in chronic heart overload

Since the first observation by Spann et al., it has become clear that in cardiac hypertrophy induced by a mechanical overloading, the velocity of shortening of the cardiac muscle (Vmax) is reduced (see ref. 2 for review). Most authors agree that this mechanical alteration is accompanied by a decrease in the Ca2+-dependent ATPase activity of myosin (see ref. 3 for review). The molecular basis of such changes was unknown because the structural modifications of the myosin molecule were ill-defined. Nevertheless, it has recently been shown that, like skeletal muscle myosin, cardiac myosin is composed of several polymorphic forms, comparable to isoenzymes. In the skeletal muscle, new functional requirements can induce changes in both contractile activity and type of myosin isoenzyme synthesised. We now report that an increase in cardiac work produced by mechanical overloading in rats induces the preferential synthesis of a cardiac myosin isoenzyme characterised by specific immunological and electrophoretic properties and exhibiting a lower ATPase activity. This adaptive change could account for the reduced shortening speed of this hypertrophied cardiac muscle.