Biomaterial Database

Purification and subunit characterization of Rhizobium meliloti RNA polymerase. 1985

B L Nielsen, and L R Brown

The RNA polymerase of the symbiotic, nitrogen-fixing bacterium Rhizobium meliloti was purified, and its subunit composition was determined. The cells were disrupted in the presence of protease inhibitors, and holoenzyme fractions were purified by fractionation by using DEAE-cellulose and DNA-agarose chromatography. The core polymerase was purified by additional chromatography on phosphocellulose. The subunit structure is beta prime (155,000 molecular weight), beta (151,000), alpha (43,000), and sigma (93,000), with an additional polypeptide of 29,000 molecular weight, which we have designated tau, found associated with both core and holoenzyme fractions. The measured stoichiometry of the holoenzyme complex was found to be 2 alpha:1 beta':1 beta:0.7 sigma:1 tau. The 93,000 molecular-weight protein subunit was identified as the sigma subunit based upon stimulation of specific transcription in assays with reconstituted polymerase.

UI	MeSH Term	Description	Entries
D008970	Molecular Weight	The sum of the weight of all the atoms in a molecule.	Molecular Weights,Weight, Molecular,Weights, Molecular
D012231	Rhizobium	A genus of gram-negative, aerobic, rod-shaped bacteria that activate PLANT ROOT NODULATION in leguminous plants. Members of this genus are nitrogen-fixing and common soil inhabitants.
D012321	DNA-Directed RNA Polymerases	Enzymes that catalyze DNA template-directed extension of the 3'-end of an RNA strand one nucleotide at a time. They can initiate a chain de novo. In eukaryotes, three forms of the enzyme have been distinguished on the basis of sensitivity to alpha-amanitin, and the type of RNA synthesized. (From Enzyme Nomenclature, 1992).	DNA-Dependent RNA Polymerases,RNA Polymerases,Transcriptases,DNA-Directed RNA Polymerase,RNA Polymerase,Transcriptase,DNA Dependent RNA Polymerases,DNA Directed RNA Polymerase,DNA Directed RNA Polymerases,Polymerase, DNA-Directed RNA,Polymerase, RNA,Polymerases, DNA-Dependent RNA,Polymerases, DNA-Directed RNA,Polymerases, RNA,RNA Polymerase, DNA-Directed,RNA Polymerases, DNA-Dependent,RNA Polymerases, DNA-Directed
D012808	Sigma Factor	A protein which is a subunit of RNA polymerase. It effects initiation of specific RNA chains from DNA.	Sigma Element,Sigma Initiation Factor,Sigma Subunit,Minor Sigma Factor,RNA Polymerase Sigma Factor H,Factor, Sigma,Factor, Sigma Initiation,Initiation Factor, Sigma,Sigma Factor, Minor,Subunit, Sigma
D013379	Substrate Specificity	A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.	Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D013698	Templates, Genetic	Macromolecular molds for the synthesis of complementary macromolecules, as in DNA REPLICATION; GENETIC TRANSCRIPTION of DNA to RNA, and GENETIC TRANSLATION of RNA into POLYPEPTIDES.	Genetic Template,Genetic Templates,Template, Genetic
D046911	Macromolecular Substances	Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.	Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular