Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The bacteriophage T4 gene 41 protein is a 5' to 3' DNA helicase which unwinds DNA ahead of the growing replication fork and, together with the T4 gene 61 protein, also functions as a primase to initiate DNA synthesis on the lagging strand. Proteolytic cleavage by trypsin approximately 20 amino acids from the COOH terminus of the 41 protein produces 41T, a 51,500-dalton fragment (possibly still associated with small COOH-terminal fragments) which still retains the ssDNA-stimulated GTPase (ATPase) activity, the 61 protein-stimulated DNA helicase activity, and the ability to act with 61 protein to synthesize pentaribonucleotide primers. In the absence of the T4 gene 32 ssDNA binding protein, the primase-helicase composed of the tryptic fragment (41T) and 61 proteins efficiently primes DNA synthesis on circular ssDNA templates by the T4 DNA polymerase and the three T4 polymerase accessory proteins. In contrast, the 41T protein is defective as a helicase or a primase component on 32 protein-covered DNA. Thus, unlike the intact protein, 41T does not support RNA-dependent DNA synthesis on 32 protein-covered ssDNA and does not stimulate strand displacement DNA synthesis on a nicked duplex DNA template. High concentrations of 32 protein strongly inhibit RNA primer synthesis with either 41 T or intact 41 protein. The 44/62 and 45 polymerase accessory proteins (and even the 44/62 proteins to some extent) substantially reverse the 32 protein inhibition of RNA primer synthesis with intact 41 protein but not with 41T protein. We propose that the COOH-terminal region of the 41 protein is required for its interaction with the T4 polymerase accessory proteins, permitting the synthesis and utilization of RNA primers and helicase function within the T4 replication complex. When this region is altered, as in 41T protein, the protein is unable to assemble a functional primase-helicase in the replication complex. An easy and rapid purification of T4 41 protein produced by a plasmid encoding this gene (Hinton, D. M., Silver, L. L., and Nossal, N. G. (1985) J. Biol. Chem. 260, 12851-12857) is also described.
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PMID:Trypsin cleavage in the COOH terminus of the bacteriophage T4 gene 41 DNA helicase alters the primase-helicase activities of the T4 replication complex in vitro. 246 40

Bacteriophage T4 gene 41 protein is one of the two phage proteins previously shown to be required for the synthesis of the pentaribonucleotide primers which initiate the synthesis of new chains in the T4 DNA replication system. We now show that a DNA helicase activity which can unwind short fragments annealed to complementary single-stranded DNA copurifies with the gene 41 priming protein. T4 gene 41 is essential for both the priming and helicase activities, since both are absent after infection by T4 phage with an amber mutation in gene 41. A complete gene 41 product is also required for two other activities previously found in purified preparations of the priming activity: a single-stranded DNA-dependent GTPase (ATPase) and an activity which stimulates strand displacement synthesis catalyzed by T4 DNA polymerase, the T4 gene 44/62 and 45 polymerase accessory proteins, and the T4 gene 32 helix-destabilizing protein (five-protein reaction). The 41 protein helicase requires a single-stranded DNA region adjoining the duplex region and begins unwinding at the 3' terminus of the fragment. There is a sigmoidal dependence on both nucleotide (rGTP, rATP) and protein concentration for this reaction. 41 Protein helicase activity is stimulated by our purest preparation of the T4 gene 61 priming protein, and by the T4 gene 44/62 and 45 polymerase accessory proteins. The direction of unwinding is consistent with the idea that 41 protein facilitates DNA synthesis on duplex templates by destabilizing the helix as it moves 5' to 3' on the displaced strand.
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PMID:Bacteriophage T4 gene 41 protein, required for the synthesis of RNA primers, is also a DNA helicase. 628 20

The dnaG gene of Escherichia coli encodes the primase protein, which synthesizes a short pRNA that is essential for the initiation of both leading and lagging strand DNA synthesis. Two temperature-sensitive mutations in the 3' end of the dnaG gene, dnaG2903 and parB, cause a defect in chromosome partitioning at the nonpermissive temperature 42 degrees. We have characterized 24 cold-sensitive suppressor mutations of these two dnaG alleles. By genetic mapping and complementation, five different classes of suppressors have been assigned; sdgC, sdgD, sdgE, sdgG and sdgH. The genes responsible for suppression in four of the five classes have been determined. Four of the sdgC suppressor alleles are complemented by the dnaE gene, which encodes the enzymatic subunit of DNA polymerase III. The sdgE class are mutations in era, an essential GTPase of unknown function. The sdgG suppressor is likely a mutation in one of three genes: ubiC, ubiA or yjbI. The sdgH class affects rpsF, which encodes the ribosomal protein S6. Possible mechanisms of suppression by these different classes are discussed.
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PMID:Isolation and characterization of suppressors of two Escherichia coli dnaG mutations, dnaG2903 and parB. 909 42

Involvement of peripheral nerves is frequent in mitochondrial disorders but with variable severity. Mitochondrial diseases causing peripheral neuropathies (PN) may be due to mutations of mitochondrial DNA (mtDNA), as is the case in MERRF and MELAS syndromes, or to mutations of nuclear genes. Secondary abnormalities of mtDNA (such as multiple deletions of muscle mtDNA) may result from mitochondrial disorders due to mutations in nuclear genes involved in mtDNA maintenance. This is the case in several syndromes caused by impaired mtDNA maintenance, such as Sensory Ataxic Neuropathy, Dysarthria and Ophthalmoplegia (SANDO) due to recessive mutations in the POLG gene, which encodes the catalytic subunit of mtDNA polymerase (DNA polymerase gamma), or Mitochondrial Neuro-Gastro-Intestinal Encephalomyopathy (MNGIE), due to recessive mutations in the TYMP gene, which encodes thymidine phosphorylase. Genetically-determined PN due to mutations of mitofusin 2, a GTPase involved in the fusion of external mitochondrial membranes, were identified during the last few years. Characteristic ultrastructural lesions (abnormalities of axonal mitochondria) are observed on longitudinal sections of nerve biopsies in patients with PN due to mitofusin 2 mutations.
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PMID:[Peripheral neuropathies due to mitochondrial disorders]. 1994 42