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Biomedical subjects

G M Edelman

Publications and source records attributed to G M Edelman.

At least 343 records · Page 19Linked to original sources
PubMed1972

The covalent and three-dimensional structure of concanavalin A.

The tentative amino-acid sequence and three-dimensional structure of the lectin concanavalin A have been determined. The amino-acid sequence, which was determined chemically, contains 238 residues. The sequences of three short stretches were assigned on the basis of x-ray crystallographic data. Interpretation of an electron density map at 2-A resolution indicates that the predominant structural element is extended polypeptide chain arranged in two anti-parallel pleated sheets or beta-structures. Residues not included in the beta-structures are arranged in regions of random coil. One of the pleated sheets contributes extensively to the interactions among the monomers to form both dimers and tetramers. The positions at which Mn(2+), Ca(2+), and saccharide are bound to the protein, and the point of cleavage for the formation of the naturally occurring fragments A(1) and A(2), have been tentatively assigned. Both metal-binding sites are at least 20-A removed from the position at which saccharides are bound. The saccharide-binding site is a deep pocket of approximately 6A x 7.5A x 18A, the inner portion of which is occupied by hydrophobic residues.

Amino Acid Sequence↗
PubMed1971

Molecular probes of spermatozoan structures.

Several methods have been devised for the isolation and labeling of structural components of spermatozoa. Rodent spermatozoa were cleaved rapidly and specifically at the junction of the heads and tails by treatment with various proteases, and the separate components were isolated by density-gradient centrifugation. Treatment with reducing agents released the mitochondrial membranes from the midpiece, exposing the underlying tail structures. Mouse spermatozoa were found to contain about 10(7) sites per cell that bind concanavalin A; most of the sites appear to be on the head, for fluorescein-labeled conjugates of concanavalin A were bound mainly to the acrosomal region. Binding of concanavalin A resulted in rapid agglutination of spermatozoa; mixed agglutinates could be formed with somatic cells, as well as with spermatozoa of other species. Fluorescent probes (naphthalenesulfonic acids) bound to the sperm plasma-membrane and caused an immediate loss of motility. In contrast, ethidium bromide bound to the nuclear structures, but did not cause immediate immobilization. These isolation and probing procedures should facilitate detailed chemical analysis of the major components of mammalian spermatozoa.

Agglutination↗
PubMed1971

Unusual fragments in the subunit structure of concanavalin A.

Gel electrophoresis in sodium dodecyl sulfate and gel filtration in guanidine. HCl indicate that native concanavalin A contains several molecular species. An intact subunit of molecular weight 27,000 has been purified from this mixture. In addition, three fragments of the intact subunit have been isolated and characterized. A working model of the concanavalin A molecule has been constructed based on pairings of the intact subunit and of subunits consisting of fragments.

Amino Acid Sequence↗
PubMed1971

Cascade chromatography and automated multidimensional fractionation.

A general method of automated multidimensional fractionation has been developed. Its basic ingredients are: (a) cascade fractionation, i.e., the sequential fractionation of components obtained from each chromatographic dimension on the same or a different dimension, (b) on-line acquisition and processing of data at each stage in the fractionation procedure, (c) a method for determining the beginning and end of each peak during column elution, and (d) automatic linkage of the successive stages in a chemical fractionation scheme based on information obtained before or during each stage. Apparatus for automatic cascade chromatography and conditional fractionation is described. The method can be extended to provide completely automatic separation of pure components from complex mixtures.

Autoanalysis↗
PubMed1971

Structure of soncanavalin A at 4 A resolution.

Concanavalin A, a phytohemagglutinin isolated from the jack bean, crystallizes at pH 6.8 in the orthorhombic space group 1222 with a = 89.9, b = 87.2, and c = 63.1 A. We have analyzed x-ray diffraction intensity data to 4 A resolution on native concanavalin A and five heavy-metal derivatives: lead, mersalyl, chloroplatinate, uranyl, and o-mercuri-p-nitrophenol. Heavy-atom positions, occupancies, and isotropic thermal parameters have been refined by least-squares methods. The electron density maps clearly show the molecular shape and the packing of the concanavalin A molecules. The asymmetric unit (mol wt 27,000) forms an elliptical dome or "gumdrop" with a base of approximately 46 x 26 A and a height of 42 A. The subunits are paired across 2-fold axes parallel to the c-axis to form dimers. The dimers are in turn paired across points of D(2) symmetry to form tetramers of roughly tetrahedral shape. Each unit has a depression located on the surface which could be the site of saccharide binding. In many regions we have been able to trace the course of the polypeptide chain.

Concanavalin A↗
PubMed1971

Cell fractionation and arrangement on fibers, beads, and surfaces.

A new method, fiber fractionation, has been used to isolate and separate cells. The cells are adsorbed to fibers covalently coupled to molecules such as antigens, antibodies, and lectins which can bind specifically to cell-surface components. The cells are then removed mechanically by plucking the taut fibers. Alternatively, competitive inhibitors of binding may be used to remove the cells at a lesser rate. Successful fractionations have been achieved by varying the degree of derivatization of the fibers by the lectin concanavalin A. Lymphoid cells have been separated by the use of different antigens coupled to the fibers. The method may also be used for specific fixation and manipulation of viable cell populations in culture. In addition to fibers, beads and surfaces have been specifically derivatized and used to achieve different geometrical arrangements of the cells.

Animals↗