Isotope labeling in solution protein assignment and structural analysis

1994 ◽  
Vol 26 ◽  
pp. 371-419 ◽  
Author(s):  
David M. LeMaster
2010 ◽  
Vol 24 (1-2) ◽  
pp. 37-43 ◽  
Author(s):  
Suren A. Tatulian

Structure determination of multidomain proteins or protein–membrane complexes is one of the most challenging tasks in modern structural biology. High-resolution techniques, like NMR or X-ray crystallography, are limited to molecules of moderate size or those that can be crystallized easily. Both methods encounter serious technical obstacles in structural analysis of protein–membrane systems. This work describes an emerging biophysical technique that combines segmental isotope labeling of proteins with Fourier transform infrared (FTIR) spectroscopy, which provides site-specific structural information on proteins and allows structural characterization of protein–membrane complexes. Labeling of a segment of the protein with13C results in infrared spectral resolution of the labeled and unlabeled parts and thus allows identification of structural changes in specific domains/segments of the protein that accompany functional transitions. Segmental isotope labeling also allows determination of the precise configuration of protein–membrane complexes by polarized attenuated total reflection FTIR (ATR–FTIR) spectroscopy. These new developments offer solutions to functionally important site-specific structural changes in proteins and protein–membrane complexes that are hard to approach using conventional methods.


2006 ◽  
Vol 44 (S1) ◽  
pp. S152-S157 ◽  
Author(s):  
Teppei Ikeya ◽  
Tsutomu Terauchi ◽  
Peter Güntert ◽  
Masatsune Kainosho

Author(s):  
W. H. Wu ◽  
R. M. Glaeser

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.


Author(s):  
E. Loren Buhle ◽  
Pamela Rew ◽  
Ueli Aebi

While DNA-dependent RNA polymerase represents one of the key enzymes involved in transcription and ultimately in gene expression in procaryotic and eucaryotic cells, little progress has been made towards elucidation of its 3-D structure at the molecular level over the past few years. This is mainly because to date no 3-D crystals suitable for X-ray diffraction analysis have been obtained with this rather large (MW ~500 kd) multi-subunit (α2ββ'ζ). As an alternative, we have been trying to form ordered arrays of RNA polymerase from E. coli suitable for structural analysis in the electron microscope combined with image processing. Here we report about helical polymers induced from holoenzyme (α2ββ'ζ) at low ionic strength with 5-7 mM MnCl2 (see Fig. 1a). The presence of the ζ-subunit (MW 86 kd) is required to form these polymers, since the core enzyme (α2ββ') does fail to assemble into such structures under these conditions.


Author(s):  
Paul DeCosta ◽  
Kyugon Cho ◽  
Stephen Shemlon ◽  
Heesung Jun ◽  
Stanley M. Dunn

Introduction: The analysis and interpretation of electron micrographs of cells and tissues, often requires the accurate extraction of structural networks, which either provide immediate 2D or 3D information, or from which the desired information can be inferred. The images of these structures contain lines and/or curves whose orientation, lengths, and intersections characterize the overall network.Some examples exist of studies that have been done in the analysis of networks of natural structures. In, Sebok and Roemer determine the complexity of nerve structures in an EM formed slide. Here the number of nodes that exist in the image describes how dense nerve fibers are in a particular region of the skin. Hildith proposes a network structural analysis algorithm for the automatic classification of chromosome spreads (type, relative size and orientation).


Author(s):  
A. J. Tousimis

The elemental composition of amino acids is similar to that of the major structural components of the epithelial cells of the small intestine and other tissues. Therefore, their subcellular localization and concentration measurements are not possible by x-ray microanalysis. Radioactive isotope labeling: I131-tyrosine, Se75-methionine and S35-methionine have been successfully employed in numerous absorption and transport studies. The latter two have been utilized both in vitro and vivo, with similar results in the hamster and human small intestine. Non-radioactive Selenomethionine, since its absorption/transport behavior is assumed to be the same as that of Se75- methionine and S75-methionine could serve as a compound tracer for this amino acid.


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