BL21/pES2KI pellets were subjected to ammonium sulfate precipitation (30-40%), resuspended in buffer A (30 mM NaCl and 20 mM Tris-Cl, pH 8.0), and applied to a Fractogel column (Merck, USA). The fraction
was eluted by a NaCl gradient (30 mM-1.4 M). After purification through a P-100 size-exclusion column (BioRad, USA), the CaroS2K fractions were Poziotinib ic50 pooled and concentrated using an Amicon centriprep-50 column (Millipore, USA) and dissolved in buffer A. BL21/pES2I pellets were precipitated by ammonium sulfate (70-100%) and resuspended in buffer A. CaroS2I purification involved a similar chromatographic procedure using the Amicon centriprep-3 column (Millipore, USA). The concentration of protein was determined by the Bradford assay (Amresco, USA). In vitro determination of Carocin S2 activity Total RNA was treated with calf intestinal alkaline phosphatase (Promega, USA) at 55°C for 30 min as recommended by the manufacturer. The reaction was arrested by adding 5 mM nitrilotriacetic acid, and RNA was extracted with equal volumes of phenol/chloroform. An aliquot of phosphatase-treated RNA was 5′-32P-labeled at 37°C for 30 min by incubation with a mixture of [γ-32P]ATP, T4 polynucleotide kinase (Promega Inc, USA), and reaction buffer in nuclease-free water . [5'-32P]Cytidine 3′,5′-bisphosphate (pCp) and T4 RNA ligase
(Promega, USA) were used for 3′-labeling of RNA . Subsequently, the mixture was purified by MicroSpin G-25 columns (GE Healthcare, USA). The purified labeled RNA was divided into aliquots and incubated without or with Carocin S2 at 28°C for
60 min, respectively. To measure Selleckchem Ceritinib its activity, CaroS2I was pre-mixed with an equal amount of CaroS2K. The mixtures were subjected to electrophoresis on a 9% polyacrylamide gel (19:1) containing 7M urea, 50 mM Tris, 50 mM boric acid, and 1 mM EDTA, pH 8.3. All samples were electrophoresed at 15℃ by PROTEIN II xi (BioRad, USA). To confirm DNase activity, 1 μg of genomic DNA from SP33 in solution containing Fossariinae buffer A was incubated with or without Carocin S2 at 28°C for 90 min. An equal quantity of genomic DNA was digested with EcoRI at 28°C for 90 min. Samples were then subjected to electrophoresis on 1% agarose gel. Antibiotic activity of Carocin S2 Overnight cultures of SP33 were diluted (1:100) with LB medium and grown at 28°C to a density of approximately 105 CFU ml-1. The activity of increasing concentrations of Carocin S2 on cells in suspension incubated at 28°C for 60 min was assessed. CaroS2I was pre-mixed with an equal molar ratio of CaroS2K. All reaction mixtures were spread onto LB agar plates and incubated at 28°C for 16 h. The experiment was performed three times. Colonies growing on a series of plates were respectively counted. Computer analysis of sequence data Sequencing of the DNA fragments was carried out using an ABI automated DNA sequencer 373S.