In:
Zeitschrift für Naturforschung C, Walter de Gruyter GmbH, Vol. 40, No. 3-4 ( 1985-4-1), p. 234-241
Abstract:
The influence of Mg 2+ ions on the secondary and tertiary structure of the RNA from bacteriophage MS2 was investigated by small-angle X-ray scattering and light scattering and by sedimentation experiments. The analysis of the outer part of the X-ray scattering curve obtained at low temperature in the absence of Mg 2+ yielded a cross-section radius of gyration of 0.88 nm and a mass per unit length of 1720 g mol -1 nm -1 . Very similar values for these parameters, which refer to the secondary structure of the RNA molecule, were also derived from the X-ray scattering curves obtained in the presence of different amounts of Mg 2+ (0.07 to 1 ions per nucleotide). On the contrary, the inner part of the X-ray scattering curves turned out to be highly dependent on the Mg 2+ concentration: the cross-section radius of gyration and the mass per unit length, which were determined from the scattering curves at small angles as parameters related to the tertiary structure of the RNA, amounted to 3.11 nm and 4000 g mol -1 nm -1 , respectively, in the absence of Mg 2+ and increased significantly upon raising the concentration of Mg 2+ . The increase of these structural parameters was found to be accompanied by a decrease of the overall radius of gyration (as revealed indirectly by X-ray scattering and directly by light scattering measurements) and by an increase of the sedimentation coefficient. The results from the investigations of the RNA at low temperature clearly establish the existence of double-stranded structures down to very low Mg 2+ concentrations as well as the occurrence of Mg 2+ induced changes of the tertiary structure. In the absence of Mg 2+ the RNA molecule appears to be a rodlike particle of about 300 nm length with a lateral diameter of about 9 to 11 nm. Upon addition of increasing amounts of Mg 2+ this extended structure tightens, eventually forming a coil-like particle. Previous X-ray scattering experiments with MS2 RNA at ionic strength 0.1 (Zipper, Folkhard and Clauwaert, FEBS Lett. 56, 283-287 (1975)) have already established the axial dimensions of such coil-like particles to be about 63, 31 and 14 nm. The results from supplementary X-ray scattering experiments performed at higher temperatures in the absence or presence of Mg 2+ clearly reflect the loss of secondary structure due to melting of the RNA. This loss is, however, less pronounced at higher concentrations of Mg 2+ .
Type of Medium:
Online Resource
ISSN:
1865-7125
,
0939-5075
DOI:
10.1515/znc-1985-3-417
Language:
English
Publisher:
Walter de Gruyter GmbH
Publication Date:
1985
detail.hit.zdb_id:
2078107-6
SSG:
12
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