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Biomedical subjects

G Alcaraz

Publications and source records attributed to G Alcaraz.

25 records · Page 2Linked to original sources
PubMed1985

Dissociation of the receptor for immunoglobulin E in mild detergents.

We previously showed that, in the absence of phospholipids, exposure of the tetrameric receptor for immunoglobulin E to mild detergents dissociates the intact beta chain and two gamma chains from the alpha chains. Having developed a practical method for assaying the dissociation, we have now explored a variety of different detergents, detergent concentrations, temperatures, times, salts, pHs, and other factors that influence the detergent-induced dissociation. Our findings should be useful for optimizing the stability of the receptor and for future studies on recombination of the subunits. The data suggest the following: (1) The critical perturbant is micellar detergent. (2) Unlike solubilization of membranes, where a molar ratio of micellar detergent:lipid of 2 is adequate, dissociation of the receptor is incomplete even at molar ratios of micellar detergent:receptor of greater than 10(5) and may be limited by a reversible component. (3) Detergents that are best for solubilizing membranes are also best for dissociating the receptors. (4) The latter observation and other data implicate bound lipid as stabilizing the receptor. Our findings may be applicable to the study of interactions between membrane proteins in general.

Animals↗
PubMed1984

Phase separation of the receptor for immunoglobulin E and its subunits in Triton X-114.

Above its critical micelle concentration, Triton X-114 in solution forms two phases at room temperature: a lower phase containing supramicellar aggregates and an upper phase largely depleted of detergent. This property of the detergent is potentially useful for separating under mild conditions proteins that bind detergent from those that do not (Bordier, C. (1981) J. Biol. Chem. 256, 1604-1607). We studied the distribution of the receptor for immunoglobulin E (IgE) and its subunits in the two phases. IgE and IgE complexed either with intact receptors or with the alpha chains of the receptor alone are principally partitioned into the upper phase, whereas the unliganded receptor as well as the isolated alpha, and especially the beta and gamma chains of the receptor, preferentially partition into the lower detergent phase. Chromatography of IgE and of the subunits of the receptor on a hydrophobic support showed that the beta and gamma chains have a considerably greater hydrophobic surface than the alpha chains or IgE. These results indicate that the distribution of a protein in the two phases of phase-separated Triton X-114 is not an all-or-none effect based upon whether it binds detergent or not. Rather, it reflects the overall balance between the hydrophobic and hydrophilic properties of the protein's surface.

Animals↗
PubMed1981

Rat IgD myeloma protein: cell-free translation of the delta mRNA and biochemical analysis of intracellular and membrane delta chain.

The analysis of IgD molecules produced by the tumor-derived IR 731 cell line showed that these molecules are not secreted and are only present at the cell surface as covalent dimers of 48 000 dalton delta chains. The original IR 731 tumor secreted complete IgD; thus, the disppearance of secretion in the cell line was correlated with the absence of light chain synthesis. The mRNA coding for the cell line delta chain was isolated and translated. The analysis of the translated delta chain (mol. wt.: 40 000) confirmed the absence of a region having the size of a domain as previously shown by partial amino acid sequence. The observation that the absence in delta chain of this region, which comprises most of the CH2 domain, could be a general feature of murine species is discussed.

Animals↗
PubMedDate not supplied

Partial structure of a rat IgD molecule with a deletion in the heavy chain.

The isolation, purification and characterization of the rat IR-731 monoclonal immunoglobulin is reported. The molecule is IgD-like, as appreciated from immunochemical and biochemical characteristics. H and L chains, Fab and Fc tryptic fragments have been isolated, analyzed, and partial sequence data have been obtained, including most cysteyl-containing peptides. The heavy chain contains a deletion which encompasses most of the CH2 domain and the beginning of the CH2 domain, and observation which does not reflect the intron-exon organization depicted for some murine heavy chains at the gene level. Basic structural features of the hinge region of the IgD molecule (extreme susceptibility to proteolytic enzymes, presence of basic amino acids near its COOH-terminus) have been found for the IR-731 molecule. In addition, partial sequence of the light chains points to the existence of K subgroups in the rat. Very limited amino acid changes have been identified in the K constant region, suggesting a possible--but limited--polymorphism which might be isotypic and/or allotypic in nature.

Amino Acid Sequence↗