Bacterial polymerase

PHA is produced in Alcaligenes eutrophus from acetyl CoA in three steps and the last step is the chain growth polymerization of hydroxyalkanoate CoA esters catalyzed by PHA polymerase (synthase), yielding PHA of high molecular weight. Kinetics and mechanism of the polymerization of hydroxyalkanoyl CoA monomers with this bacterial polymerase have been investigated. 

Automated programmable instruments that can carry out the repeated thermal cycles necessary for PCR and that can accommodate multiple samples simultaneously are now widely available. The procedure is usually performed with thermostable DNA polymerases. PCR is widely used to facilitate detection of minute amounts of viral DNA. The technique can also be used to detect specific point mutations, provided the approximate site of mutation is known. One limiting feature of this approach arises from the fact that the bacterial polymerases frequently make errors when synthesizing new strands and so can introduce mutations that are not present in the original sample. 

DNA polymerase III. This Class C enzyme is the major bacterial polymerase for DNA replication. 

Promoters for RNA polymerase II, like those for bacterial polymerases, are located on the 5 side of the start site for transcription. The results of mutagenesis experiments, footprinting studies, and comparisons of many higher eukaryotic... 

Two opposing explanations are in line with this unexpected though significant branching topology First, the Archaea and/or the Bacteria could have arisen from the Eucarya by one or two reduction events after the diversification of pol 2 and pol 3 from pol 1. The archaeal enzymes could then have been derived from pol 2/3 and the bacterial polymerases from pol 1. This reduction would include recovery of general transcription potential by one of the diversified polymerases concomitant with the loss of the other(s). This appears as unlikely as the origin of the archaeal and/or bacterial domains by reduction. 

Like prokaryotic RNA polymerase, each eukaryotic enzyme copies DNA from the 3 end, thus catalyzing mRNA formation in the 5 => 3 direction and synthesizing RNA complementary to the antisense DNA template strand. The reaction requires the precursor nucleotides ATP, GTP, CTP, and UTP and does not require a primer for transcription initiation. Unlike the prokaryotic bacterial polymerases, the eukaryotic RNA polymerases require the presence of additional initiation proteins before they are able to bind to promoters and initiate transcription. The five stages of eukaryotic transcription include initiation, elongation and termination, capping, polyadenylation, and splicing. 

In mammalian cells, although no DNA polymerase which is the equivalent of the bacterial polymerase I has been discovered, polymerases have been partially purified from, among other sources, thymus, liver, and human KB cells. Two points emerge (1) The enzyme exists in the same tissue in several forms that may be distinguished primarily by their molecular weights. The enzymes do not exhibit exonucleolytic activity although some have endonuclease activity associated with the polymerase activity. Too often the level of purification of the enzyme is too low to decide whether or not the endonucleolytic activity is a contaminant or a genuine part of the molecule. But it has been established that exonucleolytic activity is not indispen-... 

Knowledge of the molecular properties of the RNA polymerase has only begun to be accumulated. Several bacterial polymerases have been partially purified. E. coli RNA polymerase was found to be composed of several subunits ( 5) referred to as a (mol wt 39,000), jS (mol wt 155,000), and P (mol wt 165,000), a or y (mol wt 90,000), and co (mol wt 10,000). A molecule of RNA polymerase (core enzyme) contains two a-subunits, one each of / - and jS -subunits, and one or less y- or co-subunit. In addition, molecules of RNA polymerase made of the subunits described above appear to agglomerate to yield dimers (holoen-zyme) or higher polymers. Because of aggregation, molecular weight measurements have proven difficult, but it has been estimated that the active monomeric size is 330,000-390,000. 

Polysaccharides are available from plants (starch, cellulose, alginate), animals (chitin), fungi (pullulan) and bacteria (dextran, emulsan, pectin). For a sununary on industrial polysaccharides see Stivala et al. [4, S]. Proteins are produced by all living species in order to maintain their metabolic functions, but from a materials point of view it is the fibrous proteins from plants (soy), animals (wool, silk) [6] and bacteria (polyglutamic acid) that are exploited. Lignin, a polyphenolic compound, [7] and natural rubber, a polyisoprene, [8] are synthesized by plants. Finally, poly(hydroxyalkanoates) are synthesized naturally exclusively by bacteria [9]. Bacterial polymerase genes have also been successfully transferred to plants [10]. 

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