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Biomedical subjects

K E Narva

Publications and source records attributed to K E Narva.

7 recordsLinked to original sources
PubMed1991

New classes of Streptomyces coelicolor A3(2) mutants blocked in undecylprodigiosin (Red) biosynthesis.

Fifteen mutants of Streptomyces coelicolor A3(2) blocked in both the bipyrrole branch (redA) and a second site specific to the undecylprodigiosin pathway were characterized. Some of the mutants were ordered biosynthetically based on cosynthesis experiments. Complementation of each of the mutants with wild-type DNA cloned in low- and high-copy number plasmid vectors allowed the mutants to be separated into 12 new classes which are physically clustered within approximately 37 kb on the S. coelicolor genome. Early-step biosynthetic genes are centrally located and are flanked by later-step and regulatory genes.

DNA, Bacterial↗
PubMed1990

Nucleotide sequence and transcriptional analysis of the redD locus of Streptomyces coelicolor A3(2).

Previous genetic evidence suggested that the redD gene product might be involved in the regulation of undecylprodigiosin (Red) biosynthesis in Streptomyces coelicolor. The redD+ gene was subcloned on a 2.2-kilobase-pair restriction fragment from the S. coelicolor redCD region by complementation of S. coelicolor JF1 (redD42). The DNA sequence of the 2.2-kilobase-pair redD-complementing region was determined, and the redD coding sequence was identified by computer analysis and deletion subcloning. Transcription at the redD locus was analyzed by using in vivo promoter probing, high resolution S1 mapping, and in vitro runoff transcription. A face-to-face arrangement of promoters was deduced, in which the proposed redD promoter was opposed by a cluster of four other promoters for another unidentified open reading frame. In time course experiments, redD transcription preceded that at two biosynthetic loci, redE and redBF; transcription at the latter two loci was reduced in redD42 mutants. The putative redD polypeptide lacked any strong sequence similarities to other known proteins.

Base Sequence↗
PubMed1988

The amino acid sequence of the eukaryotic DNA [N6-adenine]methyltransferase, M.CviBIII, has regions of similarity with the prokaryotic isoschizomer M.TaqI and other DNA [N6-adenine] methyltransferases.

The sequences of the genes coding for M.CviBIII (from virus NC-1A which infects a eukaryotic alga) [Narva et al., Nucleic Acids Res. 15 (1987) 9807-9823] and M.TaqI (from the bacterium Thermus aquaticus) [Slatko et al., Nucleic Acids Res. 15 (1987) 9781-9796] have been determined recently. Both enzymes methylate adenine in the sequence TCGA. We have compared the predicted amino acid sequences of these two methyltransferases (MTases), with each other and with ten other N6 A-MTases and find regions of similarity. M.CviBIII and M.TaqI were most closely related followed by M.PaeR7, whose recognition sequence (CTCGAG) contains the M.TaqI/M.CviBIII recognition sequence TCGA, and M.PstI, whose recognition sequence is CTGCAG. All of the N6-MTases contain the sequence Asp/Asn-Pro-Pro-Tyr (B-P-P-Y) referred to by Hattman et al. [J. Bacteriol. 164 (1985) 932-937] as region IV. The predicted secondary structure of this region forms a finger-like structure ('beta finger') containing a beta-pleated sheet (...XXXB), two beta-turns (P-P) followed by another beta-pleated sheet [Y/FXXX...].

Amino Acid Sequence↗
PubMed1987

Molecular cloning and characterization of the gene encoding the DNA methyltransferase, M.CviBIII, from Chlorella virus NC-1A.

The gene encoding the DNA methyltransferase, M.CviBIII, from Chlorella virus NC-1A was cloned and expressed in E. coli plasmid pUC8. Plasmid (pNC-1A.14.8) encoded M.CviBIII methylates adenine in TCGA sequences both in vivo in E. coli and in vitro. Transposon Tn5 mutagenesis localized the M.CviBIII functional domain to a 1.5 kbp region of pNC-1A.14.8 and also indicated that a virus promoter directs transcription of the gene in E. coli. The 2.1 kbp insert containing the M.CviBIII gene was sequenced and a single open reading frame of 1131 bp was identified within the domain determined by Tn5 mutagenesis. When the M.CviBIII gene was fused in-frame with the 19 amino-terminal codons of lacZ a 45 kD polypeptide was identified in maxicells as predicted by the DNA sequence. The M.CviBIII gene was not essential for virus replication since a virus M.CviBIII deletion mutant also replicated in Chlorella.

Amino Acid Sequence↗