Beta-lactamase expression in Streptomyces cacaoi

Substrate analysis and molecular cloning of the extracellular alkaline phosphatase of Streptomyces griseus

Streptomyces species secrete large amounts of alkaline phosphatase (AP) enzymes that have not been characterized so far. An AP has been purified to homogeneity from cultures of Streptomyces griseus IMRU 3570. The enzyme has a monomer size of 62 kDa and is processed in the culture to a 33 kDa protein as shown by immunoblotting. The enzyme was purified by ammonium sulfate precipitation, CM-Sephadex cationic exchange, chromatofocusing and HPLC Sphaerogel 3000SW filtration. The pure enzyme uses a variety of organic phosphorylated compounds as substrates. The N-terminal end of the mature protein was found to be RLREDPFTLGVASGDPHP. The gene phoA has been cloned using as probe an oligomer based on the N-terminal sequence of the S. griseus AP. phoA encodes a protein of 62678 Da with low homology to the AP of Escherichia coli. The phoA gene was found to be homologous to three alkaline-phosphatase-encoding genes previously identified in the Streptomyces coelicolor genome. On the basis of the optimal pH, substrate specificity and differences in amino acid sequence of motifs defining the active centre of APs, the S. griseus AP uses a wide range of organic phosphate substrates and is different from the phosphatases of Gram-negative bacteria.

[Genetic and biochemical studies on the regulatory mechanism of the self-resistance and biosynthesis of antibiotics]

The following topics are described: 1. chemistry of beta-lactamases; 2. beta-lactamases from Streptomyces including distribution of beta-lactamases in actinobacteria, properties of beta-lactamases from Streptomyces, cloning and regulatory mechanism of expression of beta-lactamase genes from Streptomyces and evolution and classification of beta-lactamases in general; 3. penicillin-binding proteins from Streptomyces including beta-lactam-producing- and non-producing strains and 4. eukaryotic-type protein kinases from Streptomyces including cloning of the genes and evolution and classification of eukaryotic-type protein kinases in general.

Cloning, sequence and expression of the argG gene from Streptomyces lavendulae

The argG gene, encoding argininosuccinate synthetase, was cloned from Streptomyces lavendulae KCCS0055 by colony hybridization using the argG-carrying 2.1-kb fragment of S. coelicolor DNA as a probe. The restriction map of the cloned DNA fragment was very similar to that of S. coelicolor. This DNA fragment could complement the argG mutation of both S. lividans 1326 I10 and Escherichia coli K-12 JE5694, suggesting that the fragment contained a promoter for both E. coli and S. lividans. The subcloning experiment using E. coli K-12 JE5694 as a host has indicated that the essential region for argG is contained in the 2.5-kb DNA fragment. The translational product was identified as a 56-kDa kDa protein in minicells and by conventional gel electrophoresis. Determination of the nucleotide (nt) sequence of the 2.5-kb DNA fragment revealed one open reading frame of 1449 bp. The amino acid (aa) sequence analysis showed that the N-terminus was Ser, and 9 aa from the N terminus were completely identical with those deduced from the nt sequence. Nuclease S1 mapping indicated that the transcription start point is located near the start codon.

Sequence of a gene encoding beta-lactamase from Streptomyces cellulosae

The nucleotide sequence of beta-lactamase (Bla)-encoding gene, bla, from Streptomyces cellulosae KCCS0127 was determined. The deduced amino acid sequence was very close to that of class-A Bla, especially those from Streptomyces species, but completely different from class-D Bla. This is contrary to the result expected from its substrate specificity and its property of binding blue dextran and NADP+.

Induction of a Streptomyces cacaoi beta-lactamase gene cloned in S. lividans

The previously cloned class A beta-lactamase gene (bla) of Streptomyces cacaoi was shown to be inducible by beta-lactam compounds in the host organism S. lividans. A regulatory region of 2.75 kb was identified and the nucleotide sequence determined. It contained four open reading frames (ORFs) of which only two were complete and required for induction. ORF1-ORF2 exerted a positive regulatory effect on the expression of bla. Inactivation of ORF1 or of ORF2 resulted not only in the loss of induction, but also in a 30- to 60-fold decrease in the basal (non-induced) level of beta-lactamase production. ORF1 codes for a DNA-binding protein related to the AmpR repressor/activator, which controls the expression of ampC (class C beta-lactamase) genes in several Enterobacteria.

Nucleotide sequence and transcriptional analysis of activator-regulator proteins for beta-lactamase in Streptomyces cacaoi

The nucleotide sequence of the 2.7-kb DNA fragment upstream of the structural gene of beta-lactamase in Streptomyces cacaoi was determined. Computer-aided "FRAME" analysis revealed four possible open reading frames (ORFs), three in one direction and one in the opposite direction. One of them (ORF1, BlaA) encoded an activator-regulator protein whose deduced amino acid sequence was similar to that of other activator-regulator proteins in bacteria. Insertion of an 8-bp BamHI linker into the BlaA region decreased the beta-lactamase activity sharply, from 50 U to 1 U/ml. This protein (BlaA) was found to bind to the nucleotide sequence between the bla (beta-lactamase structural gene) and blaA genes. Another ORF (ORF2, BlaB) in the same orientation had a couple of amino acid sequences similar to that of pBR322 beta-lactamase. However, insertion of the 8-bp BamHI linker indicated that this ORF was functional as an activator-regulator but not as a beta-lactamase. Therefore, there were two activator-regulator proteins in the upstream region of the structural gene of the beta-lactamase. Nuclease S1 mapping predicted that transcription for the activator proteins commenced at the translational initiation codon or within a few nucleotides from the translational start site. Transcription was in the opposite direction to that of the beta-lactamase structural gene.

Compilation and analysis of DNA sequences associated with apparent streptomycete promoters

The DNA sequences associated with 139 apparent streptomycete transcriptional start sites are compiled and compared. Of these, 29 promoters appeared to belong to a group which are similar to those recognized by eubacterial RNA polymerases containing sigma 70-like subunits. The other 110 putative promoter regions contain a wide diversity of sequences; several of these promoters have obvious sequence similarities in the -10 and/or -35 regions. The apparent Shine-Dalgarno regions of 44 streptomycete genes are also examined and compared. These were found to have a wide range of degree of complementarity to the 3' end of streptomycete 16S rRNA. Eleven streptomycete genes are described and compared in which transcription and translation are proposed to be initiated from the same or nearby nucleotide. An updated consensus sequence for the E sigma 70-like promoters is proposed and a potential group of promoter sequences containing guanine-rich -35 regions also is identified.