The complete amino acid sequence of actins from bovine aorta, bovine heart, bovine fast skeletal muscle, and rabbit slow skeletal muscle. A protein-chemical analysis of muscle actin differentiation

Actin typing on total cellular extracts: a highly sensitive protein-chemical procedure able to distinguish different actins

Based on the finding that the amino-terminal tryptic peptide of actin is a reliable marker for actin divergence, we describe in detail a highly sensitive protein-chemical procedure for actin typing. The method is performed on non-radioactivity labeled cells and tissues and six actins can be identified unambiguously in warm-blooded vertebrates. The method is quantitative and gives directly the ratio of the different actions in the specimens. It does not require previous purification of actin and can be used on total cellular extracts without any prior fractionation. The procedure can be extended to actins not previously characterized by amino acid sequence analysis and makes certain predictions possible about the partial amino acid sequences of the amino-terminal tryptic peptides, mostly sufficient for a correlation with DNA sequences derived from cloned actin genes. This is done as an example for the cytoplasmic action present in Schneider L-2 Drosophila melanogaster cells. Although the method is currently used routinely on 10(5) cells, modifications are discussed, which should allow the analysis to be performed with even higher sensitivity.

Purification of actin from cardiac muscle

Actin from cardiac acetone and ether powders is compared to actin from skeletal acetone powder using a modification of an established extraction procedure. The yield of actin from cardiac ether powder is nearly the same as the yield from skeletal acetone powder whereas significantly less actin is obtained from cardiac acetone powder. Sodium dodecyl sulfate polyacrylamide gel electrophoresis shows the actins from each of the sources to be virtually identical in terms of purity and mobility. Molecular sieve chromatography of G-actin demonstrates cardiac actin from ether powder to have identical polymerization and mobility properties as skeletal actin from acetone powder. A simplified procedure, developed for highly purified actin from muscle powder and prepared in a single day is presented. The storage of F-actin at -80 degrees C is also discussed.

Permanently proliferating rat vascular smooth muscle cell with maintained expression of smooth muscle characteristics, including actin of the vascular smooth muscle type

Cells of an established clonal line (RVF-SMC) derived from rat vena cava are described by light and electron microscope methods and biochemical analysis of the major proteins. The cells are flat, and they moderately elongate and form monolayers. They are characterized by prominent cables of microfilaments bundles decoratable with antibodies to actin and alpha-actinin. These bundles contain numerous densely stained bodies and are often flanked by typical rows of surface caveolae and vesicles. The cells are rich in intermediate-sized filaments of the vimentin type but do not show detectable amounts of desmin and cytokeratin filaments. Isoelectric focusing and protein chemical studies have revealed actin heterogeneity. In addition to the two cytoplasmic actins, beta and gamma, common to proliferating cells, two smooth muscle-type actins (an acidic alpha-like and a gamma-like) are found. The major (alpha-type) vascular smooth muscle actin accounts for 28% of the total cellular actin. No skeletal muscle or cardiac muscle actin has been detected. The synthesis of large amounts of actin and vimentin and the presence of at least three actins, including alpha-like actin, have also been demonstrated by in vitro translation of isolated poly(A)+ mRNAs. This is, to our knowledge, the first case of expression of smooth muscle-type actin in a permanently growing cell. We conclude that permanent cell growth and proliferation is compatible with the maintained expression of several characteristic cell features of the differentiated vascular smooth muscle cell including the formation of smooth muscle-type actin.

Organization of actin gene sequences in the sea urchin: molecular cloning of an intron-containing DNA sequence coding for a cytoplasmic actin

Southern transfer and solution hybridization experiments, using as probe a DNA fragment that encodes for Drosophila actin, demonstrate cross hybridization to DNA from the sea urchin Strongylocentrotus purpuratus. Recombinant DNA clones that contained sea urchin genomic DNA fragments were constructed and screened for the presence of actin-encoding DNA sequences by colony hybridization with the Drosophila actin sequence. Two different putative actin-encoding clones were identified and were shown to specifically hybridize actin-encoding mRNA from a complex mRNA population. Southern blot hybridization experiments with both the Drosophila actin sequence and one of the cloned sea urchin sequences, in conjunction with solution hybridization data, suggest an actin gene copy number of 5-20 per haploid genome. DNA sequence analysis of one of the cloned sequences indicates that this fragment codes for a cytoplasmic form of actin and contains an intervening sequence of at least 200 nucleotides beginning immediately after amino acid 121 in the protein sequence.

Myosin from fetal hearts contains the skeletal muscle embryonic light chain

The contractile proteins of adult skeletal and cardiac muscle tissue are very similar. Some of these proteins are identical in amino acid sequence or differ only slightly. Various structural studies have shown that the heavy and light chains of myosin are also homologous in skeletal and cardiac muscles. In developing skeletal muscles, certain myosin subunits are present which are not found in the corresponding adult muscle. Whether fetal cardiac muscle also contains myosin subunits homologous to these early forms is not known. We now report that ventricular myosin of fetal rats has a light chain polypeptide corresponding to the skeletal muscle embryonic light chain. This result provides further evidence that a form of myosin light chain, not detectable in adult skeletal or ventricular myosin, is characteristic of the early stages of striated muscle development.

Identification of recombinant phages containing sequences from different rat myosin heavy chain genes

The construction and identification of a recombinant plasmid containing a cDNA insert which hybridizes specifically to myosin heavy chain mRNA is described. The plasmid was used as a probe to screen a rat genomic library for recombinant phages containing myosin heavy chain sequences. Six clones with approximately 15 k bp inserts each were isolated. Digestion with several restriction enzymes and hybridization of the fractionated DNA with the plasmid probe showed that the clones contained 3 different DNA inserts. Electron microscopy of a heteroduplex made by hybridization of DNA from two clones confirmed that the inserts originated in different genes. Hybridization of size-fractionated ECOR1 digested rat spleen DNA with the cloned probe suggested the existence of at least 5 myosin heavy chain genes.

Structure of a split yeast gene: complete nucleotide sequence of the actin gene in Saccharomyces cerevisiae

The complete nucleotide sequence of the actin gene from Saccharomyces cerevisiae has been determined. The coding region is interrupted by a 304-base-pair intervening sequence that is located within the triplet coding for amino acid 4. DNA sequences of the intron-exon junctions are similar to those found in higher eukaryotes and can be aligned such that the intron starts with the dinucleotide 5'-G-T-3' and ends with 5'-A-G-3'. Regions fo homology within the sequences upstream from the initiation codon and those following the termination codon have been detected between the yeast iso-1-cytochrome c gene and the actin gene. As deduced from the nucleotide sequence, yeast actin has 374 amino acid residues. Its primary structure, especially the NH2-terminal third of the protein, is highly conserved during evolution.

Vegetative Dictyostelium cells containing 17 actin genes express a single major actin

Although actin is highly conserved between different eukaryotic species, six tissue-specific actins have been characterised in higher vertebrates by complete amino acid sequence analysis (two cytoplasmic actins, two smooth muscle actins and two sarcomeric actins). Their tissue specificity suggests they may differ in some important although unknown physiological property. Actin expression in lower eukaryotes seems to be a simpler process than in higher eukaryotes since biochemical experiments have indicated only one major type in purified preparations from various species. However, Firtel et al. have isolated several recombinant plasmids containing sequences of Dictyostelium discoldeum DNA complementary to actin messenger RNA and have suggested that this unicellular slime mould may have 17 actin genes potentially giving rise to several different actins. We have, therefore, determined the complete amino acid sequence of actin from vegetative Dictyostelium cells. This sequence is unique and agrees with the DNA sequences of four actin genes for that region of the DNA, which is currently known. The protein sequence does not agree with the three other 'genes' and we discuss the possible expression of minor actin species.

Molecular cloning of the actin gene from yeast Saccharomyces cerevisiae

Two overlapping DNA fragments from yeast Saccharomyces cerevisiae containing the actin gene have been inserted into pBR322 and cloned in E.coli. Clones were identified by hybridization to complementary RNA from a plasmid containing a copy of Dictyostelium actin mRNA. One recombinant plasmid obtained (pYA102) contains a 3.93-kb Hindlll fragment, the other (pYA208) a 5.1-kb Pstl fragment, both share a common 2.2-kb fragment harboring part of the actin gene. Cloned yeast actin DNA was identified by R-loop formation and translation of the hybridized actin mRNA and by DNA sequence analysis. Cytoplasmic actin mRNA has been estimated to be about 1250 nucleotides long. There is only one type of the actin gene in S.cerevisiae.