Size and charge isomer separation and estimation of molecular weights of proteins by disc gel electrophoresis

Role of the receptor in the mechanism of action of adenosine 3':5'-cyclic monophosphate

Highly purified cAMP-dependent protein phosphokinase from adrenal-cortical tissue contains cAMP-receptor activity. In activating the kinase, cAMP binds to the receptor and causes it to dissociate from its complex with the kinase. The kinase, freed of receptor, is fully activated and no longer stimulable by cAMP. Kinase can be similarly activated by differentially denaturing the receptor with heat. Addition of receptor suppresses kinase activity; this suppression can be overcome by cAMP. After dissociation of receptor, two molecular forms of the activated kinase exist. The cAMP receptor thus functions as a repressor of the protein kinase; binding of cAMP to receptor causes it to dissociate from the kinase, which is then fully activated.

Immunological and biophysical separation of dengue-2 antigens

Antigenic compositions of slowly sedimenting dengue-2 hemagglutinin (SHA) and soluble complement-fixing antigen (SCF) were compared with the virion (rapidly sedimenting hemagglutinin, RHA) by radioimmune precipitation (RIP), RIP inhibition, kinetic neutralization, and neutralization blocking tests with the use of hyperimmune mouse ascitic fluids. RHA and SHA were unable to inhibit completely the RIP of each other by anti-RHA, and neutralization by anti-RHA was not blocked by SHA. This indicated that SHA is serologically related, but not identical, to RHA. SHA differed from RHA in that SHA lacked the "core" polypeptide but contained the two envelope polypeptides. In addition, SHA contained a polypeptide with a molecular weight of 16,500 daltons and a suggestion of several other proteins. These data, when considered with other evidence, suggest that SHA is a special form of "incomplete virus." SCF was unable to inhibit the RIP of SHA or RHA or to block neutralizing antibodies. Further, anti-SCF did not neutralize RHA or precipitate significant levels of SHA or RHA. Polyacrylamide gel electrophoresis separated SCF from structural polypeptides by molecular size. This evidence suggests that SCF is a nonstructural antigen.

Glycyl-tRNA synthetase: an oligomeric protein containing dissimilar subunits

Glycyl-tRNA synthetase from Escherichia coli is a tetramer containing two small (33,000 daltons) and two large (80,000 daltons) subunits. The subunits can be separated and then reassembled to form active enzyme. Genetically altered glycyl-tRNA synthetases are modified in either the large or the small subunit. Wild type activity can be reconstituted in vitro by mixing extracts containing enzymes with modifications in different subunits.

Anaphylatoxin inactivator of human plasma: its isolation and characterization as a carboxypeptidase

The failure of human serum to give rise to anaphylatoxin activity could be attributed to the presence of a potent inactivator of anaphylatoxin in human serum. The inactivator was isolated and characterized as an alpha-globulin with a molecular weight of approximately 310,000. It was found to abolish the activity of both anaphylatoxins, which are derived respectively from the third and the fifth component of complement, and of bradykinin. Inactivation of C3-derived anaphylatoxin and of bradykinin was accompanied by release of C-terminal arginine from these peptides. The anaphylatoxin inactivator was shown to hydrolyze the synthetic substrates hippuryl-L-arginine and hippuryl-L-lysine and to be inhibited by ethylenediaminetetraacetate (EDTA) or phenanthroline. These observations indicate that the anaphylatoxin inactivator constitutes a metal-dependent enzyme resembling in specificity pancreatic carboxypeptidase B.