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R Malathi

Publications and source records attributed to R Malathi.

24 records · Page 2Linked to original sources
PubMed1985

Backbone conformation in nucleic acids: an analysis of local helicity through heminucleotide scheme and a proposal for a unified conformational plot.

A relationship has been established to express the local helicity of a polynucleotide backbone directly in terms of the virtual bonds spanning the conformationally equivalent heminucleotide repeats, with a view to provide a better understanding of the cumulative effects of all the chemical bond rotational variations on local helicity. Using this, an analysis made with a few oligodeoxynucleotide crystal structures clearly brings forth that it is the concerted movements manifested in the near neighbour correlations between the pair of chemical bonds C4'-C5' and P-O5' and C4'-C3' and P-O3' of the 5' and 3' heminucleotides respectively that are primarily responsible for the observed non-uniform helical twists both in A and B type helical backbones. That these need not be restricted to oligodeoxynucleotides but may be a feature of oligoribonucleotides backbone also is shown from an analysis of helical segments of yeast tRNA(Phe). A proposal of a unified or a grand two dimensional conformational plot which would help visualise succinctly the overall effect of the variations in all the repeating six chemical bonds of a polynucleotide backbone is made. Apart from considerable simplification, the plot affords identification on it regions characteristic of helical, and loop and bend conformations of nucleic acid backbone chain.

Base Sequence↗
PubMed1984

Tertiary structure of tRNAPhe. A possible correlation between the structural functional unit of this tRNA and its exonic sequence.

It has been shown recently [Go (1981) Nature (London) 291, 90-92; Blake (1983) Trends Biochem Sci. 8, 11-13] that the exonic regions of the genes of proteins haemoglobin, lysozyme and immunoglobin correspond closely to the compactly folded structural units. Despite the absence of classical domain structures in tRNA compared with those found in several proteins, close inspection of certain features in the distance maps obtained for yeast tRNAPhe using the conformationally equivalent heminucleotide scheme reveals that a similar situation might also be present in ribonucleic acids such as tRNA species and the exonic sequences of their genes. Also it seems possible that certain segments of yeast tRNAPhe may be characterized as possessing a domain-like character, and this seems to provide stereochemical support for possible conservation of L-shape structure for tRNA species lacking the entire dihydrouridine arm such as those found in mitochondria.

Base Sequence↗
PubMed1982

Secondary and tertiary structural foldings in tRNA. A diagonal plot analysis using the blocked nucleotide scheme.

A distance plot obtained using the blocked nucleotide concept, which regards the repeating nucleotide moieties to be made up of two blocks of nearly equal magnitude, has permitted us to visualize the polynucleotide backbone folding in yeast tRNAPhe. The plot clearly manifests medium- and long-range tertiary interactions involving various structural domains. Apart from the well known T psi-D loop interactions, other long-range interactions associated with the variable loop as well as the D loop are explicitly seen. Most importantly, the plot reveals an approximate two-fold symmetry in the molecule between the domains related to the tertiary interactions in addition to the symmetry between long helical domains. The different patterns on the plot are interpreted in terms of helix-helix, loop-helix and loop-loop interactions.

Methods↗