Showing papers by "Laboratory of Molecular Biology published in 1976"
TL;DR: Electrostatic stabilization is an important factor in increasing the rate of the reaction step that leads to the formation of the carbonium ion intermediate, found in the cleavage of a glycosidic bond by lysozyme.
3,951 citations
TL;DR: A large selection of the 3′ non-coding regions of rabbit and human globin mRN As are 85% homologous, demonstrating that this region is significantly conserved in evolution.
Abstract: The sequence A–A–U–A–A–A is present in six different purified messenger RNA molecules (specifically the α- and β-globulin mRNAs of rabbit and human, the immunoglobulin light chain mRN A of mouse (MOPC 21) and the ovalbumin mRN A of chicken) about 20 residues away from the 3′-terminal poly(A) sequence. In addition, a large selection of the 3′ non-coding regions of rabbit and human globin mRN As (both the α- and β- globin mRN As) are 85% homologous, demonstrating that this region is significantly conserved in evolution.
2,447 citations
TL;DR: Cell fusion techniques have been used to produce hybrids between myeloma cells and antibody‐producing cells that are permanently adapted to grow in tissue culture and are capable of inducing antibody-producing tumors in mice.
Abstract: Cell fusion techniques have been used to produce hybrids between myeloma cells and antibody-producing cells. The hybrid lines derived are permanently adapted to grow in tissue culture and are capable of inducing antibody-producing tumors in mice. Spleens from mice immunized against sheep red blood cells (SRBC) were fused to an 8-azaguanine-resistant clone (X63-Ag8) of MOPC 21 myeloma. Over 50% of the derived hybrid lines produce and secrete immunoglobulins different from the MOPC 21 myeloma. About 10% of the hybrid lines exhibit anti-SRBC activity. The high proportion of antibody-producing hybrids suggests that the fusion involves a restricted fraction of the spleen cell population, probably cells committed to antibody production. In order to avoid the presence of the MOPC 21 heavy chain in the specific hybrids, another myeloma cell line (NSI/1-Ag4-1) has been used. This is a nonsecreting variant of the MOPC 21 myeloma which does not express heavy chains. Three anti-SRBC (probably of the mu, gamma2b and gamma1 classes, respectively) and two anti-2,4,6-trinitrophenyl (of the mu class) antibody-producing hybrids have been repeatedly cloned. By random selection and by selection of specific clones according to their lytic activity (clone plaque selection), a number of different lines have been constructed. Such lines express different combinations of the four possible chains of each hybrid line: the myeloma gamma and K chains and the specific antibody heavy and light chains. In three cases (Sp1, Sp2 and Sp7) it is shown that only the specific H and L combination has activity and that the myeloma chains are unable to substitute for them. In most cases lines have been derived which no longer express the MOPC 21 chains but only the specific antibody chains.
2,170 citations
TL;DR: A simple diagrammatic representation has been used to show the arrangement of α helices and β sheets in 31 globular proteins, which are classified into four clearly separated classes.
Abstract: A simple diagrammatic representation has been used to show the arrangement of α helices and β sheets in 31 globular proteins, which are classified into four clearly separated classes. The observed arrangements are significantly non-random in that pieces of secondary structure adjacent in sequence along the polypeptide chain are also often in contact in three dimensions.
1,197 citations
TL;DR: This work shows how the concept of time-averaged forces can be used to simplify conformafional energy calculations on globular proteins and shows that the simplifications work well in representing the stable native conformation of this globular protein.
1,089 citations
TL;DR: The defects in two nonsecreting variant clones of the mouse plasmacytoma MOPC 21 (P3) were studied by tissue culture methods and the variants (NSI and NSIII) do not synthesize detectable heavy chains.
Abstract: The defects in two nonsecreting variant clones of the mouse plasmacytoma MOPC 21 (P3) were studied by tissue culture methods. The variants (NSI and NSIII) do not synthesize detectable heavy chains. NSI synthesizes, but does not secrete, light chains and NSIII does not synthesize light chain. A screening procedure was used allowing the detection of revertant cells secreting immunoglobulin. The method is based on a hemolytic plaque assay using anti-immunoglobulin-coated red cells. No revertants were detected among 2 x 10(7) cells. Both variant lines were fused to another myeloma line (PI) which secretes a complete immunoglobulin and excess light chains. Analysis of the products by isoelectric focusing showed that in the hybrids there was no reactivation of synthesis of the nonexpressed chains. The defects leading to loss of synthesis cannot therefore be complemented in the hybrid lines. The secretion of light chain in NSI, on the other hand, could be complemented in the hybrid but the light chain was only secreted as part of a new immunoglobulin hybrid molecule.
725 citations
TL;DR: The complete, primary chemical structure of a viral genome has now been established and biological properties, such as ribosome binding and codon interactions can now be discussed on a molecular basis.
Abstract: Bacteriophage MS2 RNA is 3,569 nucleotides long. The nucleotide sequence has been established for the third and last gene, which codes for the replicase protein. A secondary structure model has also been proposed. Biological properties, such as ribosome binding and codon interactions can now be discussed on a molecular basis. As the sequences for the other regions of this RNA have been published already, the complete, primary chemical structure of a viral genome has now been established.
698 citations
TL;DR: The anatomy of the pharynx of Caenorhabditis elegans has been reconstructed from electron micrographs of serial sections, and some interpretations of how these neurones function have been offered.
Abstract: The anatomy of the pharynx of Caenorhabditis elegans has been reconstructed from electron micrographs of serial sections. The pharynx is used for pumping food into the gut, and is composed of 34 muscle cells, 9 marginal cells, 9 epithelial cells, 5 gland cells and 20 neurones. Three regions of specialization in the cuticle lining of the pharyngeal lumen may aid in the accumulation of food particles. A basement membrane isolates the pharynx from the rest of the animal, making the pharyngeal nervous system a nearly self-contained unit which is composed primarily of five classes of motor neurones and six classes of interneurones. Three other classes have also been described, which by their morphology appear to be neurosecretory and motor, motor and interneuronal, and lastly one pair that only innervates three of the marginal cells. Some classes of neurone have free endings just under the cuticle lining the lumen of the pharynx, suggesting that these are mechano- or proprio-receptive endings. The connectivity of these neurones has been described at the level of individual synaptic regions, and after combining this information with video taped observations of the pharynx pumping, some interpretations of how these neurones function have been offered.
660 citations
TL;DR: The nervous system of Caenorhabditis elegans is arranged as a series of fibre bundles which run along internal hypodermal ridges and three of the motor neurone classes receive their synaptic input from a set of interneurones coming from the nerve ring.
Abstract: The nervous system of Caenorhabditis elegans is arranged as a series of fibre bundles which run along internal hypodermal ridges. Most of the sensory integration takes place in a ring of nerve fibres which is wrapped round the pharynx in the head. The body muscles in the head are innervated by motor neurones in this nerve ring while those in the lower part of the body are innervated by a set of motor neurones in a longitudinal fibre bundle which joins the nerve ring, the ventral cord. These motor neurones can be put into five classes on the basis of their morphology and synaptic input. At any one point along the cord only one member from each class has neuromuscular junctions. Members of a given class are arranged in a regular linear sequence in the cord and have non-overlapping fields of motor synaptic activity, the transition between fields of adjacent neurones being sharp and well defined. Members of a given class form gap junctions with neighbouring members of the same class but never to motor neurones of another class. Three of the motor neurone classes receive their synaptic input from a set of interneurones coming from the nerve ring. These interneurones can in turn be grouped into four classes and each of the three motor neurone classes receives its synaptic input from a unique combination of interneurone classes. The possible developmental and functional significance of these observations is discussed.
643 citations
TL;DR: A simple, rapid, highly sensitive and reproducible assay for angiotensin-converting enzyme in untreated serum is described, useful for the diagnosis and possible management of sarcoidosis and may have other applications in the future.
Abstract: A simple, rapid, highly sensitive and reproducible assay for angiotensin-converting enzyme in untreated serum is described. It is based on the conversion of the substrate analog, hippuryl-L-histidyl-L-leucine (5 mM in 0.1 M K phosphate, pH 8.3-0.3 M NaCl) to hippurate and L-histidyl-L-leucine, which is quantified spectrofluorimetrically (lamdba excitation = 360 nm; lamdba fluorescence = 500 nm) by formation of a fluorescent adduct with ophthaldialdehyde. The chloride requirement and inhibition and activation patterns correspond to those for angiotensin-converting enzyme. The Km for hippuryl-L-histidyl-L-leucine was 1.33 mM. The mean value of serum angiotensin-converting enzyme for 58 normal human subjects (mean age, 32 years; range 19-57) was 32.2 +/- 1.30 (SE), with a standard deviation of 9.87 nmol/min/ml serum. The assay is useful for the diagnosis and possible management of sarcoidosis and may have other applications in the future.
472 citations
TL;DR: It is proposed that the prelumirhodopsin intermediate contains a strained all-trans retinal molecule produced directly and rapidly from the 11-cis, 12-s-trans conformation in r Rhodopsin by a bicycle-pedal isomerisation.
Abstract: Computer simulation of the molecular dynamics of retinal during its photoisomerisation inside a restrictive active site gives a detailed model for the sequence of events in the first step of the vision process. It is proposed that the prelumirhodopsin intermediate contains a strained all-trans retinal molecule produced directly and rapidly from the 11-cis, 12-s-trans conformation in rhodopsin by a bicycle-pedal isomerisation. The model reproduces the main experimental observations and explains how the protein makes the photoisomerisation path unique.
TL;DR: It is proposed that the seven α and seven β bands are alternative sets of sites which bind equivalently to complementary groups of sites on seven actins in the “relaxed” and “active” states of muscle, respectively.
TL;DR: Turbidometric measurements of the kinetics of filament assembly revealed a biphasic mechanism, involving the initial rate-limiting formation of a hexamer nuclear particle followed by a more rapid rate of polymerization to filaments.
TL;DR: The detailed results show that the displacement of the iron atom from the plane of the porphyrin ring increases from 0·40 to 0·55 A on going from met to deoxy.
TL;DR: Comparison with the data in the previous paper suggests that there is a relationship between the ancestry of a cell and its function and the significance of programmed cell death is discussed.
Abstract: 56 nerve cells are added to the ventral cord and associated ganglia of Caenorhabditis elegans at about the time of the first larval moult. These cells are produced by the uniform division of 13 neuroblasts followed by a defined pattern of cell deaths. Comparison with the data in the previous paper suggests that there is a relationship between the ancestry of a cell and its function. The significance of programmed cell death is discussed.
TL;DR: It is concluded that although the other histones have a role in DNA organization within the nucleosome, the arginine-rich histone pair, H3/H4, can organize DNA segments the length of theucleosome core in the absence of all otherhistones.
TL;DR: Bacteriophage φX174 genes D and E are translated from the same DNA sequence but in different reading frames, leading to confusion in the translation of these genes.
Abstract: Bacteriophage φX174 genes D and E are translated from the same DNA sequence but in different reading frames.
TL;DR: Nuclei prepared by the above method look morphologically healthy in oocytes cultured in vitro for up to one month after nuclear injection, compared with other methods, such as those involving the use of detergents, which undergo deterioration within a few days after injection into oocytes.
Abstract: A method is described by which nuclei associated with some cytoplasm can be rapidly prepared from a suspension of cells. The method involves the use of lysolecithin and bovine serum albumin. Oocytes of Xenopus laevis were injected with about 200 nuclei prepared from human He La cells by this method. Nuclei were deposited in oocyte cytoplasm, in the oocyte nucleus, or in the dispersed contents of a ruptured oocyte nucleus. Injected He La nuclei enlarge up to several hundred times in volume in the course of a few days. Their enlargement is associated with chromatin dispersion, increased binding of an acidic dye, and with the reduction in size, and eventual disappearance, of nucleoli. The amount of He La nucleus enlargement is much greater when the oocyte nucleus is ruptured. The fate of injected nuclei was followed by the use of HeLa nuclei whose DNA had been previously la belled with [ 3 H] thymidine. La belled DNA does not pass from injected He La nuclei into the oocyte nucleus. Injected nuclei appear not to fuse with each other or with the oocyte nucleus. Nuclei prepared by the above method look morphologically healthy in oocytes cultured in vitro for up to one month after nuclear injection. Nuclei prepared by other methods, such as those involving the use of detergents, undergo deterioration within a few days after injection into oocytes.
TL;DR: The experiments confirm the role of the engrailed gene in development of the posterior wing compartment and suggest that the postero-dorsal margin is primarily responsible for the control of shape, and that the ventral compartment is, to some extent, modeled on the dorsal.
TL;DR: The crystal structure of yeast tRNA Phe is refined at 2·5A resolution, using real-space refinement and improved electron density maps to confirm almost all the structural details found earlier by fitting a wire model to the map in an optical comparator.
TL;DR: TMV RNA is not an efficient template for translation of the viral coat protein, in spite of containing nucleo-tide sequences coding for the protein.
Abstract: TMV RNA is not an efficient template for translation of the viral coat protein, in spite of containing nucleo-tide sequences coding for the protein. Efficient translation requires the prior synthesis within infected cells of a smaller RNA carrying only a portion of the information encoded in the whole genome.
TL;DR: Deoxyribonuclease I causes depolymerization of filamentous muscle actin to form a stable complex of 1 mole DNAase I:1 mole actin, and heavy meromyosin binds tightly to actin filaments and blocks completely the DNA enzyme I: actin filament interaction.
TL;DR: The structure of Haemoglobin and its role in Oxygen Equilibrium and Factors Aficting the oxygen Equilibrium are described.
Abstract: 1. INTR~OUC~~N 1.1. The Structure of Haemoglobin 221 221 1.2. The Equilibrium of Haemoglobin with Oxygen 228 1.3. Factors Aficting the Oxygen Equilibrium 229
TL;DR: It is suggested that protein synthesis may have begun without even a primitive ribosome if the primitive tRNA could take up two configurations and could bind to the messenger RNA with five base-pairs instead of the present three.
Abstract: It is suggested that protein synthesis may have begun without even a primitive ribosome if the primitive tRNA could take up two configurations and could bind to the messenger RNA with five base-pairs instead of the present three. This idea would impose base sequence restriction on the early messages and on the early genetic code such that the first four amino acids coded were glycine, serine, aspartic acid and aspargine. A possible mechanism is suggested for the polymerization of the early message.
TL;DR: Regulatory light chains which bind to desensitized scallop myofibrils with high affinity and restore calcium control were found in a number of molluscan and vertebrate myosins, including Mercenaria, Spisula, squid, lobster tail, beef heart, chicken gizzard, frog and rabbit.
TL;DR: A continuous and rapid oriented flow of lipid molecules in eukaryotic plasma membranes may explain capping of surface antigens.
Abstract: A continuous and rapid oriented flow of lipid molecules in eukaryotic plasma membranes may explain capping of surface antigens.
TL;DR: Electron micrographs of tilted specimens of coated vesicles show that their coats are based on polyhedral lattices constructed from 12 pentagons plus a variable number of hexagons, which enables a variety of vesicle to be accommodated in an economical manner.
TL;DR: The N-terminal amino acid sequences of VSSAs isolated from four closely related variants are reported, and it is reported that the VSSA seems to be the major or sole constituent of the surface coat and comprises 5–10% of the total cell protein.
Abstract: THE major pathogenic African (salivarian) trypanosomes can evade the immune response through a process of antigenic variation (reviewed in ref. 1). Mainly due to Gray's work2,3, this variation is thought to be phenotypic—involving sequential expression of alternative genes and not resulting from contemporaneous mutation. The capacity for variation which exists within a clone, isolate or species, or within strains circulating within a geographical area, is uncertain (though probably extensive) and is relevant to an evaluation of the feasibility of developing vaccines. Although serotyping of trypanosome populations has been refined through the use of fluorescence methods4,5, there is a need to characterise the relevant antigens and investigate the molecular basis of antigenic variation. Other workers6–9 identified putative variable antigens and found them to be soluble glycoproteins10–12, probably located in the surface coat13,14. The antigen preparations obtained, however, were generally heterogeneous, frequently unstable or in low yield. A recent report15 described the complete purification in good yield of individual variant-specific surface antigens (VSSAs) from a series of clones of Trypanosoma brucei. The VSSAs seem to be the primary mediators of antigenic variation in T. brucei. Each anti-genically homogeneous trypanosome clone yields one predominant glycoprotein antigen composed of a single polypeptide chain (apparent molecular weight 65,000 as determined by sodium dodecyl sulphate (SDS)–polyacrylamide gel electrophoresis) and, depending on the variant, 7–17% (w/w) carbohydrate (unpublished results of J. G. Johnson). The VSSA seems to be the major or sole constituent of the surface coat and comprises 5–10% of the total cell protein. Studies of the amino acid sequences, carbohydrate constitution and cell-surface organisation of several VSSAs are in progress, and we report here the N-terminal amino acid sequences of VSSAs isolated from four closely related variants.
TL;DR: An electron density map of the TMV disk at 5 Å resolution has been obtained using isomorphous replacement and non-crystallographic symmetry and the polypeptide chain can be traced with little ambiguity.
Abstract: An electron density map of the TMV disk at 5A resolution has been obtained using isomorphous replacement and non-crystallographic symmetry. The polypeptide chain can be traced with little ambiguity. The axial contacts between protein subunits are unlike those in the virus, the disk being a more open structure apparently designed for rapid interaction with the RNA.
TL;DR: The results strongly support the previous conclusion that the arginine-rich histones are unique in their ability to create, with DNA a structure with many features of native chromatin.