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Biomedical subjects

L Hirth

Publications and source records attributed to L Hirth.

At least 73 records · Page 4Linked to original sources
PubMed1976

RNA viruses: stabilization of brome mosaic virus.

The relative importances of protein-protein and RNA-protein interactions in stabilizing the architecture of brome mosaic virus particles are discussed in the light of the following experimental evidence: (a) disassembly pathways of the virus particles, (b) reassembly of the virus and self-association capacity of the protein moiety, and (c) the role of divalent cations in virus stabilization, and their relevance to localization of the RNA in the virus particles. Evidence is given that the capsid of BMV is primarily stabilized by hydrophobic bonds at low pH, but not around and above neutrality where RNA-protein electrostatic interactions are essential to the integrity of the virus particles. A model is proposed for the structure of BMV in the different configurational states.

Capsid↗
PubMed1976

Nature and specificity of the RNA-protein interaction in the case of the tymoviruses.

Dissociation-reassociation experiments performed with turnip yellow mosaic virus in the presence of various RNAs and polynucleotides were used to investigate the degree of specificity and the contribution of the associated RNA moiety to the stability of TYMV. The results emphasize the importance of strategic cytosine residues spread along the RNA chain. Some insight into the contribution of the protein could be gained from comparison of TYMV and eggplant mosaic virus (EMV), a virus similar to TYMV although its top component contains low molecular mass RNA's able to bind various amino acids. Hydrophobic interactions between protein subunits are less important in EMV than in TYMV, and artificial capsids could be obtained from dissociated EMV coat protein. Whether the capsid is or is not the precursor of the virion in tymovirus morphogenesis is discussed.

Amino Acids↗
PubMed1976

Specific encapsidation of fragments of TMV RNA.

The in vitro reconstitution of tobacco mosaic virus (TMV) is initiated by the binding of a disk of TMV protein to the 'disk recognition site', a region of the RNA chain at or near the 5'-terminus for which the disk has special affinity. In order to gain insight into the recognition process, we have studied the ability of disks to encapsidate short RNA fragments produced by partial pancreatic or T1 RNase digestion of TMV RNA. The disk is capable of dicriminating among such fragments, encapsidating only a few of the many present in the digest. The products of encapsidation are short nucleoprotein rods of the same diameter as TMV and of length proportional to that of the encapsidated RNA fragment. The particles differ from TMV, however, in one significant aspect (apart from their length): they possess rings of RNA-free protein at one or both extremities of the rod. In the case of T1 RNase digestion the principal encapsidated fragments were fragments T1 (105 nucleotides) and a family of smaller fragments containing elements of the same sequence. Partial digestion with pancreatic RNase generated only one major fragment (fragment P1; 150 nucleotides) with affinity for the disk. Fragment T1 has been sequenced and shown to represent a portion of the coat protein cistron. Fragment P1 has been partially sequenced but its function is not yet known. Several lines of evidence indicate that fragment T1 is not the disk recognition site. The portion of the TMV RNA chain from which fragment P1 is derived, on the other hand, is encapsidated early in the reconstitution process; thus fragment P1 may contain the disk recognition site. Fragment T1 and fragment P1 both have purine-rich and cytosine-poor sequences near their termini. In addition, fragment T1, and possibly fragment P1, possess a periodicity of order three in purine residues. It seems likely that one or both of the aforesaid properties are largely responsible for the affinity of these fragments for the disk.

RNA, Viral↗
PubMed1976

Stucture of the amino-acid accepting 3'-end of high-molecular-weight eggplant mosaic virus RNA.

The sequence of the first 59 nucleotides from the 3'-OH terminus of high-molecular-weight eggplant mosaic virus RNA has been determined by standard radio-chemical techniques. The fragment was identified among the products of partial T1 RNase digestion by making use of the reverse migration, at pH 2.5, of the 3'-OH terminal oligonucleotide. No abnormal bases were found. A model of secondary structure may be constructed for this fragment, which is known to fix valine in the presence of valyl-tRNA synthetase. Its relation to the structures of genuine tRNAs and to the 3'-OH termini of other viral RNAs that also accept amino acids is discussed.

Amino Acids↗
PubMed1976

Physical and functional heterogeneity in TYMV RNA: evidence for the existence of an independent messenger coding for coat protein.

Turnip yellow mosaic virus RNA can be separated into two distinct components of 2 times 10(6) and 300 000 daltons molecular weight after moderate heat treatment in the presence of SDS or EDTA. The two species cannot have arisen by accidental in vitro degradation of a larger RNA, as they both possess capped 5' ends. Analysis of the newly synthesized proteins resulting from translation of each RNA by a wheat germ extract shows that the 300 000 molecular weight RNA can be translated very efficiently into coat protein. When translated in vitro the longer RNA gave a series of high molecular weight polypeptides but only very small amounts of a polypeptide having about the same mass as the coat protein. Thus our results suggest that the small RNA is the functional messenger for coat protein synthesis in infected cells.

Genetic Code↗
PubMed1976

Some properties of tobacco protoplast chromatin.

Chromatin was prepared from tobacco-leaf protoplasts. Its solubility in increasing molarities of NaCl was studied and the structure of the soluble fraction observed by electron microscopy. We demonstrate that in plants, the DNA and histones are associated in beaded structures similar to those called omicron-bodies or nucleosomes in animal chromatin. The nucleosomes were associated with DNA in either compact or extended forms. The compact arrangement was predominant in the fraction solubilized between 0.1 and 0.4 M NaCl. The extended form, present at 0.5 and 0.6 M NaCl. showed DNA filaments of various lengths interspacing the nucleosomes. At these ionic strengths ring structures were present, associated with the DNA. At 0.7 M NaCl and above, only DNA filaments were present, occasionally associated with big rings, and nucleosomes were compoetely dissociated. Free DNA molecules were present at all ionic strengths used. The possible origin and significance of the rings are discussed.

Cell Nucleus↗
PubMed1975

[Lip prints--variability and genetics (author's transl)].

In a sample of 500 persons, including 76 families with 133 children, 22 mono- and 17 dizygote twins, lip prints were prepared for the study of variability and genetical basis of ridge-pattern in the region of mucous membrane lips. Taking 4 classes of pattern with different ridge-branching as a basis we observed more frequently branched pattern at the upper lip and mainly simple pattern at the lower lip. About 30% of the lip-prints showed whirling figures--at the upper lip simple and median, at the lower lip double and paramedian. Investigations during several months showed stability against environmental factors. The results of twins, families and mother(father)-child combinations proved a genetical basis of lip-prints. Applications of cheiloscopy to genetical investigations are reported.

Adolescent↗