Isolation and characterization of a DNA-uptake-stimulating protein from the culture medium of Neurospora crassa slime strain.

A protein fraction was purified to homogeneity from the culture medium of the wall-less (slime) strain of Neurospora crassa (FGSC 1118), which proved to be identical with DNA-uptake-stimulating factor (designated DUSF), which has been described earlier [Schablik, M. and Szabó, G. (1981) FEMS Microbiol. Lett. 10, 395-397]. The quantity of DUSF is measured by the amount of [3H]DNA uptake by Neurospora cells at standard conditions. Its relative molecular mass was 230,000. It has an isoelectric point of pH 5.5. This protein consists of two identical subunits, relative molecular mass 110,000.

Protein patterns of Streptomyces griseus strains during development.

Protein patterns from mycelial extracts of Streptomyces griseus strains No. 45H and No. 52-1 were studied by one dimensional gradient PAGE with 20 cm run. The results are reproducible, the protein patterns are the same for the same developmental stage in a given strain. There are well-defined characteristic changes of the protein patterns during the life cycle. The proteins of spores show conspicuous differences compared to protein patterns of the old (72 h) mycelia in the same culture. There is no difference between protein patterns of spores from submerged and from solid media. The protein patterns of two closely related Streptomyces griseus strains significantly differ from each other. After pulse labelling with (14C)-labelled protein hydrolyzate for 40 min, the specific activities of the proteins show considerable differences. There are characteristic bands with low specific activity and others with high incorporation. The fluorograms of the 16, 40 and 64 h cultures show that different proteins are being synthesized intensively at different ages of the culture.

Comparison of protein patterns of Streptomyces griseus spores from surface and submerged cultures.

Protein patterns of conidia produced by a Streptomyces griseus strain in submerged cultures and on solid media were compared. Cell-free extracts (30 000 X g supernatant) were prepared and analyzed on gradient SDS polyacrylamide gels. The protein patterns of both kinds of conidia were found to be practically identical, and they differed from protein patterns of the old vegetative hyphae in a characteristic way.

A substance effecting differentiation in Streptomyces griseus. Purification and properties.

A conidium-producing variant of Streptomyces griseus, strain 45-H, produces a substance, factor C, which is capable of inducing conidium formation in the hyphae of a conidium-non-producing mutant, strain 52-1. Factor C can be determined quantitatively on the basis of this biological effect. The biologically active substance can be purified by ion-exchange chromatography on cellulose phosphate combined with affinity chromatography on DNA-agarose. The purified substance is concentrated at least 1700 times. The molecular weight of factor C, estimated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, is about 34500. On determining the amino acid composition of factor C 60% of the amino acids were found to be hydrophobic.

Ribosomal proteins from vegetative hyphae and from spores of Streptomyces griseus.

Ribosomes from vegetative cells and spores of Streptomyces griseus have been used to prepare ribosomal proteins for polyacrylamide gel electrophoresis. Differences in the gel electrophoretic profile of proteins from vegetative cells and spore ribosomes can be detected. Spore ribosomes were stable during the isolation process, but in the case of vegetative cell ribosomes it was necessary to use protease inhibitor to obtain reproducible results. Suspensions of washed ribosomes of vegetative hyphae have higher proteolytic activity than ribosomes from spores.