Transport of labeled folic acid (PteGlu), pteroylpolyglutamates (PteGlu,.,), 5-methyl-tetrahydrofolate (5.methylHPteGlu), and methotrexate in late-log phase cells of Lacfobacillus casei was active, and subject to inhibition by unlabeled pteroyhnonoglutamates, pteroylpolyglutamates, and iodoacetate, but not glutamate or glutamate dipeptides. Pteroylpolyglutamates were transported without prior h...

A two-phase system in vitro has been developed for studying the bone-mobilizing effects of parathyroid hormone. Phase I consists of the incubation of hormone with ascites cells, and Phase II is the incubation of Phase I supernatant with dead bone powder. The mobilization of labeled calcium from this powder is the index of hormonal activity. The response to hormone is apparent at lo-* M hormone,...

The synthesis of 2-oxo-cis-4-hexenoic acid from DL-2amino-cis-4-hexenoic acid is described. The ~0x0 acid appears to exist at neutral pH largely in the dienolic form. Ultracentrifuged extracts of steroid-induced Pseudomonas iestosteroni rapidly converted 2-oxo-cis-4-hexenoic acid-lw to wo*. The same enzyme preparations, when supplemented with NAD and a NADPH-generating system, have been previou...

Plasma membranes isolated from bovine corpora lutea showed specific binding with 1251-human chorionic gonadotropin and 1251-human luteinizing hormone; unlabeled hormones competitively inhibited the binding. The binding of the 1251-human chorionic gonadotropin to the receptor was a saturable phenomenon and the half-saturation was attained at a concentration of 4 X lo-r0 M. Maximum hormone recept...

A number of mutant Chinese hamster ovary (CHO) cell lines resistant to the cytotoxic action of n-amanitin have been isolated. The a-amanitin sensitivity of the different mutant cell lines varied widely, but correlated well with the au-amanitin sensitivity of the RNA polymerase II activity in each of these mutant cell lines. In comparison with the RNA polymerase II of wild-type cells, three muta...

Purified yeast phenylalanyl transfer RNA synthetase can aminoacylate three Escherichia co2i transfer RNAs. One of these tRNAs is E. coli valine transfer RNA which has been extensively purified and shown capable of being aminoacylated with phenylalanine and purified yeast phenylalanyl-tRNA synthetase. The extent of this heterologous aminoacylation is approximately 90%. A comparison of the struct...

Bovine plasminogen activator was isolated from a mixture of streptokinase and human plasminogen. The method of preparation was based on the difference in solubility between the activator and its precursors. The activator can be prepared from either crude or highly purified streptokinase and highly purified human plasminogen. The activator complex gave a single component in starch gel electropho...

The existence of protonated hydroxymethylamines of sec+ ondary amines, RzNHCHtOH, in equilibrium with hydroxymethylamines and protonated amines, has been demonstrated by titration at equilibrium and by rapid titration of the protonated hydroxymethylamines. Analogous compounds, . R3NCHeOH, are formed from formaldehyde and the sterically favorable tertiary amines: pyridine, iv-methylimidazole, an...

A glycoprotein was isolated from human group 0 erythrocyte membranes previously treated with detergents by a mild extraction with 90% phenol and further purified by successive passages through columns of DEAE-, CM-Sephadex, and Sephadex G-100 followed by a chloroform-methanol extraction. The purified glycoprotein appeared to be a single molecular species in gel filtration, polyacrylamide electr...

Enzymatic activity was measured by following both the disappearance of substrate, CMP-[14C]sialic acid, and the appearance of product, [14C]sialic acid, after separation by ion exchange column chromatography. The stoichiometry of this relationship was 1: 1. The activity of CMP-sialic acid hydrolase in crude homogenates of rat liver (in 0.25 M sucrose) was 53 units of enzyme per g of liver. The ...