title: The RNA polymerase of marine cyanophage Syn5.
abstract: A single subunit DNA-dependent RNA polymerase was identified and purified to apparent homogeneity from cyanophage Syn5 that infects the marine cyanobacteria Synechococcus. Syn5 is homologous to bacteriophage T7 that infects Escherichia coli. Using the purified enzyme its promoter has been identified by examining transcription of segments of Syn5 DNA and sequencing the 5'-termini of the transcripts. Only two Syn5 RNAP promoters, having the sequence 5'-ATTGGGCACCCGTAA-3', are found within the Syn5 genome. One promoter is located within the Syn5 RNA polymerase gene and the other is located close to the right genetic end of the genome. The purified enzyme and its promoter have enabled a determination of the requirements for transcription. Unlike the salt-sensitive bacteriophage T7 RNA polymerase, this marine RNA polymerase requires 160 mm potassium for maximal activity. The optimal temperature for Syn5 RNA polymerase is 24 °C, much lower than that for T7 RNA polymerase. Magnesium is required as a cofactor although some activity is observed with ferrous ions. Syn5 RNA polymerase is more efficient in utilizing low concentrations of ribonucleotides than T7 RNA polymerase.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA. Bin_Zhu@hms.harvard.edu
authors.forename: Bin
authors.initials: B
authors.lastname: Zhu
authors.forename: Stanley
authors.initials: S
authors.lastname: Tabor
authors.forename: Desislava A
authors.initials: DA
authors.lastname: Raytcheva
authors.forename: Alfredo
authors.initials: A
authors.lastname: Hernandez
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: King
authors.forename: Charles C
authors.initials: CC
authors.lastname: Richardson
mesh_terms: D059001:Aquatic Organisms / Q000821:virology*; D001435:Bacteriophages / Q000187:drug effects / Q000201:enzymology*; D001483:Base Sequence; D003067:Coenzymes / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000302:isolation & purification / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D008670:Metals / Q000494:pharmacology; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics; D012265:Ribonucleotides / Q000494:pharmacology; D012492:Salts / Q000494:pharmacology; D046940:Synechococcus / Q000821:virology*; D013696:Temperature; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D003067:Coenzymes; D004279:DNA, Viral; D008670:Metals; D012265:Ribonucleotides; D012492:Salts; D012321:DNA-Directed RNA Polymerases