SUMMARY: Arginine and methionine transport by Aspergillus nidulans mycelium was investigated.
A single uptake system is responsible for the transport of arginine, lysine and ornithine. Transport is energy-dependent and specific for these basic amino acids. The K m value for arginine is 1 x 10-5 M, and V max is 2.8 nmol/mg dry wt/min; K m for lysine is 8 x 10-6 M; K i for lysine as inhibitor of arginine uptake is 12 μM, and K i for ornithine is 3 mM.
On minimal medium, methionine is transported with a K m of 0.1 mM and V max about 1 nmol/mg dry wt/min; transport is inhibited by azide. Neutral amino acids such as serine, phenylalanine and leucine are probably transported by the same system, as indicated by their inhibition of methionine uptake and the existence of a mutant specifically impaired in their transport.
The recessive mutant nap3, unable to transport neutral amino acids, was isolated as resistant to selenomethionine and p-fluorophenylanine. This mutant has unchanged transport of methionine by general and specific sulphur-regulated permeases.
SUMMARY: Rabbit antisera against L-asparaginase preparations from Escherichia coli, Erwinia carotovora, Citrobacter sp. and Chromobacterium violaceum showed on immunoelectrophoresis that only the enzymes from E. coli and Citrobacter are immunologically related. Purified preparations had to be used to determine the immunological cross-reactions. Immunoelectrophoresis at different pH values yielded the zero mobility points of the enzymes. The activity of the Er. carotovora preparation was enhanced up to fourfold by homologous antiserum but not by normal sera. Heterologous antisera also enhanced, but only at a higher concentration. Less enhancement was observed for the other enzymes with antisera as well as with bovine serum albumin. Inhibition was not observed.
SUMMARY: Rifampicin at a concentration of 10 μg/ml completely inhibited protein synthesis in exponential-phase cultures of Bacillus amyloliquefaciens. At this same concentration the drug was shown to have no effect on the stability of mRNA, determined as the functional and hybridizable material, when compared with hybridizable mRNA in an uninhibited system. In each case, the half-life of the mRNA had a value in the range 5 ± 1 min, at 30 °C.