Reversible acetylation on Lys501 regulates the activity of RNase II

RNase II, a 3′ to 5′ processive exoribonuclease, is the major hydrolytic enzyme in Escherichia coli accounting for ∼90% of the total activity. Despite its importance, little is actually known about regulation of this enzyme. We show here that one residue, Lys501, is acetylated in RNase II. This modification, reversibly controlled by the acetyltransferase Pka, and the deacetylase CobB, affects binding of the substrate and thus decreases the catalytic activity of RNase II. As a consequence, the steady-state level of target RNAs of RNase II may be altered in the cells. We also find that under conditions of slowed growth, the acetylation level of RNase II is elevated and the activity of RNase II decreases, emphasizing the importance of this regulatory process. These findings indicate that acetylation can regulate the activity of a bacterial ribonuclease.     

Ellagic acid 4-O-rutinoside from pods of Prosopis juliflora

From the pods of Prosopis juliflora a new glycoside, ellagic acid 4-O- rutinoside, has been characterized.     

Rapid purification of a restriction endonuclease from Escherichia coli RY13

Summary A two step method for the purification of restriction endonuclease Eco RI was developed. The first step involved the purification of the enzyme on Cibacron Blue-F3GA-agarose column, followed by a hydroxyapatite column. The enzyme was homogeneous on SDS-PAGE and completely free from contaminating nucleases and phosphatases, and can be used for direct DNA hydrolysis.     

Correction to: Voltammetric detection of anti-HIV replication drug based on novel nanocomposite gold-nanoparticle–CaCO3 hybrid material

Bioprocess and Biosystems Engineering - The Figs. 2, 4 and 5 were published wrongly in this paper, due to inadvertent compilation of figures during uploading the paper.     

Design,synthesis and ex vivo evaluation of colon-specific azo based prodrugs of anticancer agents

Colon-specific azo based prodrugs of anticancer agents like methotrexate (6), gemcitabine (7) and analogue of oxaliplatin (RTB-4) (8) were synthesized and characterized by modern analytical techniques. The prepared prodrugs were stable in acidic (pH 1.2) and basic (pH 7.4) buffers which showed their stability in upper GIT environment. Further, an assay was performed which demonstrated the presence of azoreductase enzyme in the rat fecal material, rat cecum content and other parts of intestinal content which reduce specifically the azo bond and release the drug. The in vitro cytotoxicity assay was also performed which clearly indicated that these azo based prodrugs are active against human colorectal cancer cell lines (COLO 205, COLO 320 DM and HT-29). The release behavior of prodrugs (10, 11 and 15) was 60–70% after 24 h incubation at 37 °C. Therefore, the synthesized azo linked prodrugs of methotrexate, gemcitabine and RTB-4 are the potential candidates for colon targeted drug delivery system with minimal undesirable side effects.     

Nerve-muscle interaction: changes in the cellular organization of a skeletal muscle upon denervation

The alterations in the organization of lumbrical muscle of the rat have been investigated following denervation, with emphasis on the structure of cytoplasmic constituents, sarcolemma in the synaptic and non-synaptic regions and acetylcholinesterase activity. The appearance of 15--18 nm intramenbranous particles in the non-synaptic sarcolemma is thought to be related to the known acetylcholine extrajunctional sensitivity which is manifested after denervation. The acetylcholinesterase activity is greatly reduced in the synaptic region in the denervated muscle. These changes are discussed in relation to the known physiological and biochemical data.     

Substitution of lysine 213 with arginine in penicillin-binding protein 5 of Escherichia coli abolishes D-alanine carboxypeptidase activity without affecting penicillin binding.

All penicillin-binding proteins (PBPs) contain a conserved box of homology in the carboxyl-terminal half of their primary sequence that can be Lys-Thr-Gly, Lys-Ser-Gly, or His-Thr-Gly. Site-saturation mutagenesis was used to address the role of the lysine residue at this position (Lys213) in Escherichia coli PBP 5, a D-alanine carboxypeptidase enzyme. A soluble form of PBP 5 was used to replace Lys213 with 18 other amino acids, and the ability of these mutant proteins to bind [3H]penicillin G was assessed. Only the substitution of lysine with arginine resulted in a protein that was capable of forming a stable covalent complex with antibiotic. The affinity of [14C]penicillin G for the arginine mutant was 1.2-fold higher than for wild-type PBP 5 (4.4 versus 5.1 micrograms/ml for 20 min at 30 degrees C), and both proteins showed identical rates of hydrolysis of the [14C]penicilloyl-bound complex (t1/2 = 9.1 min). Surprisingly, the arginine-substituted protein was unable to catalyze D-alanine carboxypeptidase activity in vitro, which suggests that there is a substantial difference in the geometries of the peptide substrate and penicillin G within the active site of PBP 5.