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Biomedical subjects

G W Litman

Publications and source records attributed to G W Litman.

At least 127 records · Page 7Linked to original sources
PubMed1975

Analysis of polypeptide disposition in human erythrocyte membranes employing membrane inversion.

High resolution segregation of erythrocyte membrane polypeptides achieved by isoelectric focusing in 8 M urea was employed in conjunction with surface-restricted radioiodination to analyze the disposition of polypeptides within the human erythrocyte membrane. Several membrane polypeptides showed significant uptake of radioiodine, with the principal labeled component migrating between pH values of 3.0 and 3.5. Two approaches were taken in examining membrane polypeptide disposition on both faces of the erythrocyte membrane. Saturation labeling of the outer face of the membrane with one iodine isotope followed by cell lysis and reiodination with a second iodine isotope did not prove feasible and another procedure based on surface iodination with 125-I, formation of sealed inside-out vesicles and re-iodination with 131-I was adopted. Studies of sialic acid release from the membrane surface and trypsin cleavage of radioiodinated peptides indicated that selectively labeled, sealed inside-out vesicles had been formed. The ratio of 125-I to 131-I in membrane polypeptides separated by isoelectric focusing confirmed the existence of externally disposed, internally disposed and spanning proteins.

Cell Membrane↗
PubMed1974

A functional examination of hapten-binding derivatives from a murine myeloma protein with immunoglobulin features.

Various enzymatic derivatives of the murine myeloma protein IgA(MOPC-315) were subjected to hapten-binding quantitation and circular dichroic analysis in an attempt to ascertain the structural localization and functional definition of the immunoglobulin active site. The extrinsic Cotton effects observed with near saturation of the active site of the derivatives using epsilon-Dnp-L-lysine were qualitatively and quantitatively identical when normalized with respect to their macromolecular content of Dnp-binding sites; ellipticity maxima of 378 and 438 nm and an ellipticity minimum of 325 nm were recorded. Fluorescence quenching data confirmed the molecular nature of the derivation products of IgA(MOPC-315) but also introduced disparity with respect to binding kinetics, i.e., K values of 2.31 x 10(6), 6.62 x 10(6), and 2.06 x 10(7) M(-1) were determined for IgA(MOPC-315), Fab'(MOPC-315), and Fv(MOPC-315), respectively. We speculate that the results can be explained by possible modulating effects on haptenbinding contributed by novel conformations introduced through proteolysis.

Animals↗
PubMed1971

N-terminal amino-acid sequence of African lungfish immunoglobulin light chains.

The sequence of the N-terminal ten amino acids of the unblocked light chains derived from the low molecular weight immunoglobulin of a dipnoid fish, the African lungfish (Protopterus aethiopicus), has been determined. A degree of sequence heterogeneity as extensive as that displayed by pooled mammalian light chains was encountered. The major N-terminal sequence of the amino acids of light chains from lungfish immunoglobins can be made homologous with that of various Elasmobranchean, Chondrostean, Avian, and Mammalian species if an internal deletion of two base triplets in the gene coding for light chains from lungfish immunoglobulins is assumed. The existence of a deletion and/or insertion mechanism may have profound biological significance, since it would be ideal for the introduction of variability into immunoglobulin chains without sacrificing certain integral features of the antibody molecule.

Amino Acid Sequence↗