Aurin tricarboxylic acid, the anti-AIDS compound, prevents the binding of interferon-alpha to its receptor

Binding of HIV to its receptor, the CD4 molecule of lymphocytes, can be prevented by chemical agents. These agents could be considered as potential anti-AIDS drugs. We have shown that aurin tricarboxylic acid (ATA, 3 microM) specifically blocks the binding of gp120, the HIV coat protein, to the CD4 molecule. We have also found that ATA prevents the binding of interferon-alpha to its receptor in a dose-dependent manner (12-50 microM range). Membrane potential shift, associated with binding of interferon-alpha to its receptor, was also blocked by ATA in a dose-dependent fashion. Our results indicate that potential anti-AIDS drugs should be screened for such undesired side effects.     

Preparation of h and m antigens ofHistoplasma capsulatum free of heterologous antigens

Salt gradient elution of crude histoplasmin on CM-Sepharose CL6B at pH 3.0 was used in essentially a one-step procedure to isolate the h, m, and non-m antigens ofHistoplasma capsulatum and free them of any c antigen common to other pathogenic fungi. The h antigen fraction was pure; the isolated m and non-m antigens contained less than 0.1% of the c antigen present in the original preparation. The residual c antigen in these fractions was removed by affinity chromatography on Affigel-10 coupled to aBlastomyces dermatitidis fungal antiserum. The final preparations of h, m, and non-m were pure when tested by immunodiffusion (ID), sodium-dodecyl-sulfate-polyacrylamide-gel electrophoresis (SDS-PAGE), or electrofocusing. The antigens were serologically stable at neutral pH for at least three months at 10°C. The relative molecular weights, isoelectric points, and amino acid composition of the antigens are described.     

Response of Intracellular Proteolysis to Alteration of Bacterial Protein and the Implications in Metabolic Regulation

An assessment has been made of the extent to which the breakdown of microbial cellular proteins is regulated by their metabolic state or function. For this purpose, a number of agents and conditions that alter the synthesis, structure, or utility of cellular protein were examined for the effect on their lability. In Escherichia coli, 5-fluorouracil, p-fluorophenylalanine, norleucine, canavanine, thienylalanine, and puromycin, which engender nonfunctional cellular protein en masse, and ultraviolet irradiation increase the breakdown rate of proteins synthesized in their presence as much as two- to threefold without altering the general capacity for proteolysis. The effects are complicated by, but experimentally distinguishable from, secondary changes in proteolysis that accompany growth inhibition. In contrast, no potentiation of proteolysis is elicited by the presence of suppressor genes, by the administration of heat, or by the biosynthetic alterations attending large changes in the conditions of cultivation or by those attending bacteriophage infection. Thus, although mass perturbations in protein conformation are catabolically distinguishable, the more individual and limited conformational modifications that might occur in disuse do not appear to be the primary determinants of the protein turnover rate. In Bacillus subtilis, turnover synthesis of protein during starvation is as susceptible to treatment with actinomycin D as that during growth. Treatment alters neither the rate of intracellular proteolysis nor the catabolic pattern of the modicum of proteins that are still synthesized. It is concluded that there is no correlation between metabolic stability of protein and the stability of its messenger ribonucleic acid.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

Phylogenetic diversification of immunoglobulin genes and the antibody repertoire

Immunoglobulins are encoded by a large multigene system that undergoes somatic rearrangement and additional genetic change during the development of immunoglobulin-producing cells. Inducible antibody and antibody-like responses are found in all vertebrates. However, immunoglobulin possessing disulfide-bonded heavy and light chains and domain-type organization has been described only in representatives of the jawed vertebrates. High degrees of nucleotide and predicted amino acid sequence identity are evident when the segmental elements that constitute the immunoglobulin gene loci in phylogenetically divergent vertebrates are compared. However, the organization of gene loci and the manner in which the independent elements recombine (and diversify) vary markedly among different taxa. One striking pattern of gene organization is the "cluster type" that appears to be restricted to the chondrichthyes (cartilaginous fishes) and limits segmental rearrangement to closely linked elements. This type of gene organization is associated with both heavy- and light-chain gene loci. In some cases, the clusters are "joined" or "partially joined" in the germ line, in effect predetermining or partially predetermining, respectively, the encoded specificities (the assumption being that these are expressed) of the individual loci. By relating the sequences of transcribed gene products to their respective germ-line genes, it is evident that, in some cases, joined-type genes are expressed. This raises a question about the existence and/or nature of allelic exclusion in these species. The extensive variation in gene organization found throughout the vertebrate species may relate directly to the role of intersegmental (V<==>D<==>J) distances in the commitment of the individual antibody-producing cell to a particular genetic specificity. Thus, the evolution of this locus, perhaps more so than that of others, may reflect the interrelationships between genetic organization and function.