Showing papers by "Laboratory of Molecular Biology published in 1971"
TL;DR: Actin purified by a new, simple, and rapid purification procedure activated the ATPase activity of both heavy meromyosin and Subfragment 1 of heavy mercyosin, and this activation was not inhibited by the removal of Ca2+.
4,306 citations
TL;DR: The products of four of the six genes involved in bacteriophage T4 tail fibre assembly by sodium dodecyl sulphate-acrylamide gel electrophoresis of tail fibre mutant lysates and particles purified from them are identified, allowing the formulation in greater detail of the early stages of the fibre assembly pathway.
925 citations
TL;DR: Calculations show that gene duplication has probably not occurred in plant ferredoxins; phage Qβ and f2 coat proteins may be homologous; and repeats in cytochrome c are not statistically significant.
420 citations
TL;DR: The chemical studies indicate that these two proteins may contain a large segment of similar sequence, and the possibility that the A2 component is a fragment of A1 is considered, as well as the existence of possible isoenzymes of myosin.
418 citations
TL;DR: There is an inverse correlation between growth rate and cyclic AMP levels and contact inhibition of growth in cultured fibroblasts when many lines are compared during logarithmic growth.
412 citations
TL;DR: Physico-chemical experiments show that histones are not evenly distributed in chromatin, and about half of the DNA is “open” and not covered with proteins.
Abstract: Physico-chemical experiments show that histones are not evenly distributed in chromatin. About half of the DNA is “open” and not covered with proteins.
410 citations
TL;DR: The model suggests that chromosomal DNA falls into two classes: globular DNA (containing unpaired regions for control) and a much smaller fraction consisting of fibrous DNA which alone codes for proteins.
Abstract: The model suggests that chromosomal DNA falls into two classes: globular DNA (containing unpaired regions for control) and a much smaller fraction consisting of fibrous DNA which alone codes for proteins.
385 citations
TL;DR: The application of a method for computing three-dimensional density maps from transmission electron micrographs using Fourier transforms to negatively stained tomato bushy stunt virus is described in detail and the resulting reconstruction presented.
Abstract: An account is given of a method which has been developed for computing three-dimensional density maps from transmission electron micrographs using Fourier transforms. The reconstructions objectively combine data from several different views of one or more particles. The application to negatively stained tomato bushy stunt virus is described in detail and the resulting reconstruction presented. Projections of the reconstruction in the appropriate directions agree well with images of the virus taken from micrographs.
381 citations
TL;DR: The polypeptide part of the principal glycoprotein on the surface of human erythrocytes extends through the membrane barrier to the interior surface of the cell membrane.
Abstract: The polypeptide part of the principal glycoprotein on the surface of human erythrocytes extends through the membrane barrier to the interior surface of the cell membrane.
367 citations
TL;DR: In this paper, the Fourier transform of the image of a thin crystal of catalase, which has discrete diffraction maxima in the resolution range of 10 to 2.5 nm, as a function of defocusing, was determined by finding the relative contributions from phase and amplitude contrast.
Abstract: The effects of defocusing and spherical aberration in the electron microscope image are most simply and directly displayed in the Fourier transform of the image. We have investigated the process of image formation by determining the changes in the transform of the image of a thin crystal of catalase, which has discrete diffraction maxima in the resolution range of 10 to 2.5 nm, as a function of defocusing. The changes in amplitude and phase of these diffraction maxima have been measured and compared with the predictions of a first-order theory of image formation. The theory is generally confirmed, and the transfer function of the microscope is completely determined by finding the relative contributions from phase and amplitude contrast. A 'true' maximum contrast image of the catalase crystal, compensated for the effects of defocusing, is reconstructed from the set of micrographs in the focal series. The relation of this compensated image to individual underfocused micrographs, and the use of underfocus contrast enhancement in conventional electron microscopy, are discussed. This approach and the experimental methods can be extended to high resolution in order to compensate for spherical aberration as well as defocusing. In as much as spherical aberration is the factor presently limiting the resolution of electron lenses, this could provide a considerable extension of the resolution of the electron microscope.
339 citations
TL;DR: It is concluded that UGA suppression is carried out by a tRNATrp whose anticodon-codon recognition is altered by a change elsewhere in the molecule.
TL;DR: Fingerprint maps of labelled peptides derived from component a, the major protein component on the surface of human erythrocytes, indicate that parts of a reside on each side of the membrane.
TL;DR: The basal levels of ppGpp observed in both stringent and relaxed strains during balanced growth are, in most cases, the same, and vary inversely with the growth rate and RNA content of the cells.
TL;DR: Names are proposed for twelve of the groups of plant viruses and it is suggested that the value of these names should be tested by using them for an experimental period.
TL;DR: A very reactive, highly radioactive reagent designed to acylate amino groups has been synthesized: this compound, the sulphone of 35 S-labelled formylmethionyl methyl phosphate, cannot pass through the red blood cell membrane.
TL;DR: Evidence suggests that these regions, which can be trimmed in vitro by a nuclease activity in crude cell extracts, are involved in the control of cell tyrosine tRNA levels.
Abstract: The transcribed precursor of an E. coli tyrosine tRNA contains nucleotide sequences not found in the mature tRNA. Evidence suggests that these regions, which can be trimmed in vitro by a nuclease activity in crude cell extracts, are involved in the control of cell tyrosine tRNA levels.
TL;DR: In three steroid-resistant lymphoma cell populations specific binding was less than in the parent lines, suggesting that conversion to steroid resistance may be associated with changes in specific steroid binding.
Abstract: Mouse lymphoma cells in culture which are killed by adrenal steroids contain specific cortisol receptors that may be involved in the initial events of hormone action The similarity of these receptors to those in hepatoma tissue culture cells, where adrenal steroids induce tyrosine aminotransferase, suggests that certain aspects of steroid action are similar in the two systems In three steroid-resistant lymphoma cell populations specific binding was less than in the parent lines, suggesting that conversion to steroid resistance may be associated with changes in specific steroid binding
TL;DR: Self-assembly of the protein subunits of tobacco mosaic virus takes place by a series of steps and control of the aggregation and its consequences for virus assembly are described in the next two articles.
Abstract: Self-assembly of the protein subunits of tobacco mosaic virus takes place by a series of steps. The natural state of aggregation of TMV protein is not the helix but the 20S disk, which consists of two paired rings of seventeen sub-units each. Movement of 5 A is involved in the pairing. Control of the aggregation and its consequences for virus assembly are described in the next two articles.
TL;DR: The electron density map has been calculated at 6 A resolution for a human γG1 immunoglobulin molecule and is interpreted in terms of four possible models, of which a T-shaped model is favored.
TL;DR: Results obtained with this system suggest that the DNA of the operon contains a new regulator site, at which the cyclic AMP control system acts.
Abstract: A cell free system has been developed in which only the components of the lactose operon are required for its transcription. Results obtained with this system suggest that the DNA of the operon contains a new regulator site, at which the cyclic AMP control system acts.
TL;DR: A model is proposed to account for the mutagenic effects of halogenated and nonhalogenated pyrimidines, and it is found that halogen substituents affect base‐stacking patterns.
Abstract: The base-stacking patterns in over 70 published crystal structures of nucleic acid constituents and polynucleotides were examined. Several recurring stacking patterns were found. Base stacking in the solid state apparently is very specific, with particular modes of interaction persisting in various crystalline environments. The vertical stacking of purities and pyrimidines in polynucleotides is similar to that observed in crystals of nucleic acid constituents. Only partial base overlap was found in the majority of the structures examined. Usually, the base overlap is accomplished by positioning polar substituents over the ring system of an adjacent base. The stacking interactions are similar to those found in the crystal structures of other polar aromatic compounds, but are considerably different from the ring–ring interactions in nonpolar aromatic compounds. Apparently, dipole-induced dipole forces are largely responsible for solid-state base stacking. It is found that halogen substituents affect base-stacking patterns. In general, the presence of a halogen substituent results in a stacking pattern which permits intimate contact between the halogen atom and adjacent purine or pyrimidine rings. Considering differences in the stacking patterns found for halogenated and nonhalogenated pyrimidines, a model is proposed to account for the mutagenic effects of halogenated pyrimidines.
TL;DR: The ability of CRP to promote selected transcription is lost upon elution of the protein from phosphocellulose but activity is usually regained within 20 to 48 hours, and the preparation appears to be homogeneous as determined by sedimentation equilibrium studies, isoelectric focusing, and amino-terminal amino acid sequence analysis.
TL;DR: The reconstitution of TMV does not proceed by the stepwise addition of single protein subunits, but by the addition of preformed disks to the growing rod, which is the basis of the selectivity for viral over other RNAs.
Abstract: The reconstitution of TMV does not proceed by the stepwise addition of single protein subunits, but by the addition of preformed disks to the growing rod. The assembly is initiated by the interaction of a disk with a special sequence of about fifty nucleotides at the 5′ end of the TMV RNA. This is the basis of the selectivity for viral over other RNAs.
TL;DR: A method of analysing images from electron micrographs of biological specimens believed to possess rotational symmetry by producing a rotational power spectrum and combining just those components which are consistent with the previously determined symmetry to produce a filtered image is described.
TL;DR: The proteins synthesized by growing neurones are examined in the hope that there would be components the authors could identify and, perhaps, to which they could assign a role in neurite assembly.
Abstract: AXONAL growth from developing and regenerating nerve cells is a very rapid process. The growth rate is often as high as 50 µm/h1 and the axon that emerges from a cell less than 0.1 mm in diameter can have a final length of more than a metre. Such a vigorous process, occurring in a non-dividing cell, will probably dominate the biosynthetic activity of the neurone and it is likely that proteins made in large amounts will be major components of the growing fibres. For this reason we have examined the proteins synthesized by growing neurones in the hope that there would be components we could identify and, perhaps, to which we could assign a role in neurite assembly. We have used explanted neurones growing in tissue culture because they can be obtained largely free of other cell types; and we have chosen embryonic sympathetic neurones because of the extremely rapid outgrowth of processes which can be induced by addition of the nerve growth factor (NGF)2.
TL;DR: The results reported confirm the hypothesis that, under physiological conditions, haemoglobin binds CO(2) through the four terminal alpha-amino groups and that the two terminalalpha-aminos groups of alpha-chains are involved in the Bohr effect.
Abstract: 1. Three modified horse haemoglobins have been prepared: (i) αc2βc2, in which both the α-amino groups of the α- and β-chains have reacted with cyanate, (ii) αc2β2, in which the α-amino groups of the α-chains have reacted with cyanate, and (iii) α2βc2, in which the two α-amino groups of the β-chain have reacted with cyanate. 2. The values of n (the Hill constant) for αc2βc2, α2βc2 and αc2β2 were (respectively) 2.5, 2.0 and 2.6, indicating the presence of co-operative interactions between the haem groups for all derivatives. 3. In the alkaline pH range (about pH8.0) all the derivatives show the same charge as normal haemoglobin whereas in the acid pH range (about pH6.0) αc2βc2 differs by four protonic charges and αc2β2, α2βc2 by two protonic charges from normal haemoglobin, indicating that the expected number of ionizing groups have been removed. 4. αc2β2 and αc2βc2 show a 25% decrease in the alkaline Bohr effect, in contrast with α2βc2, which has the same Bohr effect as normal haemoglobin. 5. The deoxy form of αc2βc2 does not bind more CO2 than the oxy form of αc2βc2, whereas αc2β2 and α2βc2 show intermediate binding. 6. The results reported confirm the hypothesis that, under physiological conditions, haemoglobin binds CO2 through the four terminal α-amino groups and that the two terminal α-amino groups of α-chains are involved in the Bohr effect.
TL;DR: Purified tRNATrp stimulates lysozyme synthesis 30-fold above the level seen when comparable amounts of tryptophan tRNA from the non-suppressing strain, CA244, were added; it also translates poly(U-G-A) as polytryptophan more efficiently than the su− tRNA.
TL;DR: The interconversion of the two conformations is slow; this may lead to artifacts in pre-steady-state kinetics which could be misinterpreted as evidence for intermediates.
TL;DR: Near neutral pH9 TMV protein sub-units polymerize into two-layer aggregates culminating in the 20S disk, whereas the helical rod forms cooperatively at acid pH, controlled by the state of ions of two abnormally titrating carboxyl groups.
Abstract: Near neutral pH9 TMV protein sub-units polymerize into two-layer aggregates culminating in the 20S disk, whereas the helical rod forms cooperatively at acid pH. The mode of aggregation is controlled by the state of ionization of two abnormally titrating carboxyl groups.
TL;DR: The analog seems to act by lowering the rate of synthesis of tyrosine aminotransferase, as measured by the radio-immunochemical technique, which requires incorporation of the 5-bromodeoxyuridine into cellular DNA.