Deoxyriboendonucleases with exocytoplasmic location in Streptomyces

Abstract

DNase activities that show a non-specific pattern of DNA degradation on agarose gels have been detected in six strains of Streptomyees. All the enzymes were located in the cell wall-cytoplasmic membrane space, and released after protoplast production. Synthesis of these nucleases was dependent on the composition of the growth media. Differentiation on agar plates was affected by the same nutritional conditions that regulate DNAse production. All DNases were deoxyriboendonucleases that required Mg 2+ and a low ionic concentration for optimal activity. The molecular masses of native DNases range from 37+2 to 43 +_4 kDa. The enzymes produced nicks in doublestranded DNA and were unable to digest RNA. The widespread presence, location and characteristics of such nucleases in Streptomyces suggest a common role for these enzymes.

Purification, Characterization, and Role of Nucleases and Serine Proteases in Streptomyces Differentiation

“…2 These enzymes show biochemical characteristics very suitable for the role assigned in the Streptomyces developmental cycle, since they are capable of cleaving a wide variety of nucleic acids to mononucleotides and small oligonucleotides. The exocellular nucleases (which in surface cultures remain loosely bound to the mycelium) appear to act in concert with the periplasmic nucleases, discovered initially in S. antibioticus and S. glaucescens and also detected in other Streptomyces species (29). Thus, there seems little doubt that the physiological role of these nucleases is to degrade nucleic acids in the substrate mycelium to supply building blocks for macromolecular biosynthesis in the aerial mycelium.…”

A Streptomyces glaucescens endodeoxyribonuclease which shows a strong preference for CC dinucleotide

“…32P-labelled synthetic oligonucleotides (containing 6,10,12,15,17,20, 38 or 68 residues) were used as D N A size standards. The size distribution of fragments was determined by densitometric analysis of the gels once autoradiographed.…”

“…antibioticus two nutritionally regulated endodeoxyribonucleases [3, 41. A general feature of these and other species of Siwptonzycrs is that the secretion of nucleolytic enzymes temporally precedes the cellular differentiation (aerial mycelium formation [5,6]). Both processes are controlled by analogous nutritional conditions [S, 61; it is likely that DNase synthesis and differentiation respond to common triggering mechanisms.…”

“…Both processes are controlled by analogous nutritional conditions [S, 61; it is likely that DNase synthesis and differentiation respond to common triggering mechanisms. The S. gluucescens nuclease is a unique endodeoxyribonuclease which is located outside the cellular cytoplasm in the cell-wall -membrane region and is not accompanied by a modification activity [3,6]. Its synthesis is under nutritional control (i.e.…”

“…Its synthesis is under nutritional control (i.e. it is repressed by rich nitrogen sources which promote high growth rates) and it is also related to the early stationary phase of growth [6].…”