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R P Aaronson

Publications and source records attributed to R P Aaronson.

9 recordsLinked to original sources
PubMed1984

Influenza C virus hemagglutinin: comparison with influenza A and B virus hemagglutinins.

The complete nucleotide sequence of the influenza C/California/78 virus RNA 4 was obtained by using cloned cDNA derived from the RNA segment. This gene is 2,071 nucleotides long and can code for a polypeptide of 654 amino acids. Although there are no convincing sequence homologies between RNA 4 and the hemagglutinin genes of influenza A and B viruses, we suggest, on the basis of structural features, that RNA 4 of the influenza C virus codes for the hemagglutinin. The structural features which are common to the hemagglutinins of influenza A, B, and C viruses include (i) a hydrophobic signal peptide, (ii) an arginine cleavage site between the hemagglutinin 1 and 2 subunits, (iii) hydrophobic regions at the amino and carboxyl termini of the hemagglutinin 2 subunit, and (iv) several conserved cysteine residues. Additional evidence that RNA 4 of influenza C virus codes for the hemagglutinin is that the tripeptide Ile-Phe-Gly, known to be present at the amino terminus of the hemagglutinin 2 subunit of influenza C virus, is encoded by RNA 4 at a point immediately adjacent to the presumptive arginine cleavage site. The lack of primary sequence homology between the influenza C virus hemagglutinin and the influenza A or B virus hemagglutinins, which all have similar functions, might be attributed to convergent rather than divergent evolution. However, the structural similarities among the influenza A, B, and C virus hemagglutinins strongly suggest that the three hemagglutinin genes have diverged from a common precursor.

Amino Acid Sequence↗
PubMed1982

Oligonucleotide mapping: evaluation of its sensitivity by computer-simulation.

A frequently used method of comparing large RNA molecules employs the two-dimensional display of oligonucleotides generated through the action of specific RNases (oligonucleotide mapping, fingerprinting). Using computer simulations and simple analytic expressions the number of large RNase T1-resistant oligonucleotides obtained from random RNA sequences can be estimated. The computer simulations also permit estimation of the number of large oligonucleotides which remain unchanged as random variations are introduced into a random RNA sequence. In addition, computer analysis also provides a means of estimating statistical confidence limits to be used in a quantitative comparison of fingerprints of different RNA molecules. The model shows that two RNA sequences which differ overall by 1%, 5% or 10% share, on average, only 85%, 50% or 25%, respectively, of their large oligonucleotides. Thus, the use of fingerprint analysis is recommended only when closely related RNAs or regions of RNAs are compared (sequence homology greater than 90%).

Base Sequence↗
PubMed1982

Sampling of particulate suspensions for morphological evaluation: a simple method for routine and quantitative use.

A general method for obtaining representative samples of particulate suspensions for morphologic evaluation is presented. The key to the method is the orientation of a suitable substrate for sample collection normal to an applied centrifugal field. Precise orientation is achieved by floating the substrate on a dense water-immiscible fluid of low viscosity. Centrifugation may be performed in common angle-head centrifuge rotors. Two variations of the method are described which permit direct visualization or embedding of the particulate sample. Both variations are simple, can be performed routinely, and require only small amounts of material. They can also be performed simultaneously with centrifugation of the bulk samples.

Animals↗
PubMed1981

Organization in the cell nucleus: divalent cations modulate the distribution of condensed and diffuse chromatin.

The organization of rat liver nuclei in vitro depends on the ionic milieu. Turbidity measurements of nuclear suspensions in the presence of varying concentrations of divalent cations have been correlated with nuclear ultrastructure. The concentration of MgCl2 (2 mM) at which turbidity of nuclear suspensions is maximal and chromatin condensation appears most extensive is the same concentration that reportedly (Gottesfeld et al., 1974, Proc. Natl. Acad. Sci. U. S. A. 71:2193-2197) precipitates "inactive" chromatin. Thus, a mechanism is suggested by which chromatin activity and ultrastructural organization within the nucleus may be mediated. The nuclear organizational changes attendant upon the decrease in divalent cation concentration were not entirely reversible.

Animals↗
PubMed1975

Isolation of nuclear pore complexes in association with a lamina.

Nuclear pore complexes have been isolated in association with a 150 A thick lamina by detergent and salt fractionation of nuclear envelopes from rat liver. The pore complexes exhibit characteristic morphology and appear to be attached in a highly specific orientation to the lamina, which extends over relatively large areas. The pore complex-lamina fraction is composed of three major and several minor polypeptides with little or no DNA, RNA, or phospholipid. It is suggested that the association of the pore complexes and the lamina reflects the structural arrangement of the nuclear periphery in vivo.

Animals↗
PubMed1974

On the attachment of the nuclear pore complex.

Electron microscope examination of isolated rat liver nuclei after treatment with the detergent Triton X-100 revealed the complete removal of both the inner and outer membranes of the nuclear envelope. The envelope-denuded nuclei did not show any change in either shape or internal ultrastructure. Most strikingly, the nuclear pore complexes, which in untreated nuclei appear to be integral components of the nuclear envelope, were retained in their characteristic location at the distal ends of the channels leading through the peripheral heterochromatin. Determination of the chemical composition of detergent-treated nuclei showed that over 95% of the nuclear phospholipid was solubilized, thus corroborating the morphological absence of nuclear membranes. Furthermore, detergent treatment also solubilized approximately 10% of the nuclear protein. Analysis of the solubilized protein by polyacrylamide gel electrophoresis in the presence of SDS indicated that these proteins belong to a few specific classes which presumably represent the major polypeptides of the nuclear membranes. The total absence of the nuclear envelope on both morphological and biochemical grounds supports the idea that the nuclear pore complex does not require the membranes either for attachment to the nucleus or for maintenance of its own structural integrity.

Animals↗