The binding of folyl polyglutamates by hemoglobin

Pteroyl polyglutamates bind to hemoglobin with an affinity which leaves only a minor fraction of red cell folate in the free state. This could serve as a regulating mechanism for protein synthesis in the differentiating erythroblast.     

Biosynthesis of Riboflavine in Corynebacterium Species: the Purine Precursor

Corynebacterium species lacks the ability to convert either xanthine or guanine to adenine. This defect and the use of the purine nucleoside antibiotic decoyinine, which blocks the conversion of xanthosine monophosphate --> guanosine monophosphate, permit an experimental design in which the interconversion of purines is largely prevented. Cultures of this organism were grown in the presence of decoyinine and various purine supplements. Data obtained by comparing the radioactivity incorporated from guanine-2-(14)C or xanthine-2-(14)C into bacterial guanine, xanthine, and riboflavine indicate that guanine or a close derivative of guanine is the purine precursor of riboflavine.     

An Ustilago maydis Mutant Partially Blocked in P45014DM Activity Is Hypersensitive to Azole Fungicides

An Ustilago maydis ergosterol biosynthesis mutant (A14) which is partially blocked in sterol 14alpha-demethylase (P45014DM) activity is described. This mutant accumulated the abnormal 14alpha-methyl sterols, eburicol, 14alpha-methylfecosterol, and obtusifoliol, along with significant amounts of ergosterol. Although the A14 mutant grew nearly as well as the wild type, it was impaired in cell extension growth, which indicated a dysfunction in apical cell wall synthesis. The mutant was also found to be hypersensitive to the azole fungicides penconazole and tebuconazole.     

The peracid cleavage of 5-methyltetrahydrofolic acid at the C9-N10 bridge.

5-Methyltetrahydrofolate cannot be cleaved at the C⁹N¹⁰ bond by the zinc/HCl reductive or the permanganate oxidative cleavage methods. A new method has been developed to perform this cleavage, using peracetic acid in 50% trifluoroacetic acid; the cleavage is quantitative and nondestructive of γ-glutamyl peptide bonds.     

Structural role of the polyglutamate portion of the folate found in T4D bacteriophage baseplate.

Three types of reagents were used to determine the structural role and location of the polyglutamate portion of the Escherichia coli T4D bacteriophage baseplate dihydropteroyl hexaglutamate. These reagents were examined for their effect in vitro on some of the final steps in phage baseplate morphogenesis. The reagents were (i) a series of oligopeptides composed solely of glutamic acid residues but with various chemical linkages and chain lengths; (ii) a homogeneous preparation of carboxypeptidase G1, an exopeptidase that hydrolyzes carboxyl-terminal glutamates (or aspartates) from simple oligopeptides, including the gamma-glutamyl bonds on folyl polyglutamates as well as the bond between the carboxyl group of the p-aminobenzoyl moiety and the amino group of the first glutamic acid residue of folic acid; and (iii) antisera prepared against a polyglutamate hapten. All three types of reagent markedly inhibited the attachment of the phage long tail fibers to the baseplate. Other steps in baseplate assembly such as the addition of T4D gene 11 or gene 12 products were not affected by any of these reagents. These results indicate that the polyglutamate portion of the folate is located near the attachment site on the bacteriophage baseplate for the long tail fibers.     

Enhanced bactericidal activity of platelet β-lysin forE. coli in the presence of membrane perturbation

Inhibition by sodium chloride of the growth of 19 strains ofLegionella pneumophila and of 10 strains of otherLegionella spp. was studied. Results from growth in buffered -ketoglutarate cysteine yeast extract (BAYE) broth containing 0 to 2.0% sodium chloride indicated that 15/19 laboratory strains ofL. pneumophila were capable of growing in 1.0% to 1.5% sodium chloride, whereas 4 strains ofL. pneumophila and 10 strains of 6 other species were not.L. micdadei andL. longebeachae were the most inhibited in BAYE broth, growing only in concentrations of 0.5% sodium chloride. These in vitro studies indicate thatL. micdadei andL. longbeachae might be differentiated from other species by their low tolerance to salt in BAYE broth, and thatL. pneumophila may be more tolerant to salt concentrations found in brackish water environments.     

Hexazonium pararosaniline as a fixative for animal tissues

Hexazonium pararosaniline is a valuable reagent that has been used in enzyme activity histochemistry for 50 years. It is an aqueous solution containing the tris-diazonium ion derived from pararosaniline, an aminotriarylmethane dye, and it contains an excess of nitrous acid that was not consumed in the diazotization reaction. Other investigators have found that immersion for 2 min in an acidic (pH 3.5) 0.0015 M hexazonium pararosaniline solution can protect cryostat sections of unfixed animal tissues from the deleterious effects of aqueous reagents such as buffered solutions used in immunohistochemistry, while preserving specific affinities for antibodies. In the present investigation hexazonium pararosaniline protected lymphoid tissue and striated muscle against the damaging effects of water or saline. The same protection was conferred on unfixed sections treated with dilute nitrous or hydrochloric acid in concentrations similar to those in hexazonium pararosaniline solutions. Model tissues (solutions, gels or films containing gelatin and/or bovine albumin) responded predictably to well known cross-linking (formaldehyde) or coagulant (mercuric chloride) fixatives. Hexazonium pararosaniline solutions prevented the dissolution of protein gels in water only after 9 or more days of contact, during which time considerable swelling occurred. It is concluded that there is no evidence for a “fixative” action of hexazonium pararosaniline. The protective effect on frozen sections of unfixed tissue is attributable probably to the low pH of the solution.