Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

EcoRI endonuclease mutants were isolated in a methylase-deficient background following in vitro hydroxylamine mutagenesis of plasmid pKG2 (Kuhn et al.: Gene 44:253-263, 1986). Mutants which survived high-level endonuclease expression (IPTG induction) were termed null mutants. Sixty-two of 121 null mutants tested by Western blot contained normal levels of endonuclease cross-reacting protein. The complete endonuclease gene was sequenced for 27 null mutants. This group was found to consist of 20 single base-change missense mutations, 6 double mutations, and 1 triple mutation. Ten of the 20 single mutations were clustered between residues 139 and 144. When examined with respect to the structure of the EcoRI-DNA complex (McClarin et al.: Science 234:1526-1541, 1986), these alterations were found to fall predominantly into two classes: substitutions at the protein-DNA interface or substitutions at the protein-protein (dimer) interface. Protein from several of the mutants was purified and sized by using HPLC. Wild-type EcoRI endonuclease and protein from three of the DNA interface mutations (Ala139----Thr, Gly140----Ser, Arg203----Gln) appeared to be dimeric, while protein from subunit interface mutations (Glu144----Lys, Glu152----Lys, Gly210----Arg) migrated as monomers.
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PMID:Clustering of null mutations in the EcoRI endonuclease. 283 17

The DNA sequence of the colicin M activity gene cma was determined. A polypeptide consisting of 271 amino acids was deduced from the nucleotide sequence. The amino acid sequence agreed with the peptide sequences determined from the isolated colicin. The molecular weight of active colicin M was 29,453. The primary translation product was not processed. In the domain required for uptake into cells, colicin M contained the pentapeptide Glu-Thr-Leu-Thr-Val. A similar sequence was found in all colicins which are taken up by a TonB-dependent mechanism and in outer membrane receptor proteins which are constituents of TonB-dependent transport systems. The structure of colicin M in the carboxy-terminal activity domain had no resemblance to the pore-forming colicins or colicins with endonuclease activity. Instead, the activity domain contained a sequence which exhibited homology to the sequence around the serine residue in the active site of penicillin-binding proteins of Escherichia coli. The colicin M activity gene was regulated from an SOS box upstream of the adjacent colicin B activity gene on the natural plasmid pColBM-Cl139.
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PMID:Primary structure of colicin M, an inhibitor of murein biosynthesis. 303 84

A strong association has been uncovered between DNA variation at the apolipoprotein B (apoB) locus (detectable with the restriction endonuclease XbaI) and apoB level. The findings are suggestive of associations also between this DNA polymorphism and total cholesterol as well as fasting triglyceride levels, confirming recent results reported by British workers. The data suggest that lipid/apolipoprotein associations with the XbaI polymorphism are primarily caused by an effect on apoB level. In the present and in a previously reported study we found a strong association between the XbaI polymorphism and the homospecific Ag antigenic variation in low density lipoprotein (LDL) which had previously exhibited associations with lipid levels. The present data indicate that the apoB/lipid associations of the Ag and XbaI polymorphisms may reflect the same phenomenon. The associations reported could reflect variation in an apoB domain close to Ag as well as to the XbaI restriction site that is of importance for lipid binding by apoB. Alternatively, the association of apoB level with the XbaI polymorphism (which reflects a silent third base mutation in a threonine codon) could reflect phenomena related to codon usage.
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PMID:DNA polymorphism at the apolipoprotein B locus is associated with lipoprotein level. 350 91

The product of a kanamycin resistance gene encoded by plasmid pTB913 isolated from a thermophilic bacillus was identified as a kanamycin nucleotidyltransferase which is similar to that encoded by plasmid pUB110 from a mesophile, Staphylococcus aureus. The enzyme encoded by pTB913 was more thermostable than that encoded by pUB110. In view of a close resemblance of restriction endonuclease cleavage maps around the BglII site in the structural genes of both enzymes, ca. 1,200 base pairs were sequenced, followed by amino-terminal amino acid sequencing of the enzyme. The two nucleotide sequences were found to be identical to each other except for only one base in the midst of the structural gene. Each structural gene, initiating from a GUG codon as methionine, was composed of 759 base pairs and 253 amino acid residues (molecular weight, ca. 29,000). The sole difference was transversion from a cytosine (pUB110) to an adenine (pTB913) at a position + 389, counting the first base of the initiation codon as + 1. That is, a threonine at position 130 for the pUB110-coded kanamycin nucleotidyltransferase was replaced by a lysine for the pTB913-coded enzyme. The difference in thermostability between the two enzymes caused by a single amino acid replacement is discussed in light of electrostatic effects.
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PMID:Enzymatic and nucleotide sequence studies of a kanamycin-inactivating enzyme encoded by a plasmid from thermophilic bacilli in comparison with that encoded by plasmid pUB110. 609 Apr 28

Some physico-chemical properties of endonuclease (EC 3.1.4.9) from Serratia marcescens were studied and the amino acid composition of the enzyme was determined. The protein molecule was shown to contain one SH-group and one S-S-bond, which renders it different from the well studied nuclease (EC 3.1.4.7) from Staph. pyogenes. The conditions for reconstitution of the S-S-bond by dithioerythritol for quantitative estimation of cysteine residues of the endonuclease molecule were selected. The N-terminal amino acid was found to be threonine. The UV spectra for the enzyme are typical for proteins; A 0,1% 1cm,280nm is 1.46, epsilon 25 degrees 280nm,pH7,4 is 47292 M-1 cm-1. The sedimentation coefficient in phosphate buffer sW, 20 degrees is 3.4 S, pI is 6.5 and 7.5.
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PMID:[Serratia marcescens endonuclease. Properties of the enzyme]. 627 Dec 66

Bursal lymphomas induced in chickens by avian leukosis viruses (ALVs) harbor proviral insertions that augment expression of an adjacent cellular oncogene, c-myc. To analyze such insertionally mutagenized c-myc genes in greater detail, we isolated molecular clones from two independent tumors. Precise proviral integration has occurred within the transcribed region of the c-myc gene in both mutant alleles. The proviruses bear different internal deletions that preclude the expression of the gag, pol, and env genes. The c-myc gene from bursal lymphoma LL4 contains a single copy of an ALV long terminal repeat (LTR), presumably the product of homologous recombination between LTRs at the ends of a normal provirus; the "solo" LTR is positioned in the correct orientation to act as a promoter for the c-myc gene. Bursal lymphoma LL3 contains an ALV provirus positioned upstream in the opposite transcriptional orientation to the coding exons of c-myc and deleted from a site within the leader region into the gag gene. In addition, the nucleotide sequence of the c-myc gene from tumor LL3 differs from the published sequence of the normal c-myc coding region at 3 positions of 180 determined. One of these changes, a silent nucleotide transition, is documented as a somatic mutation by restriction endonuclease mapping. It is flanked by two other candidate tumor-specific point mutations, one of which predicts an amino acid replacement, Pro----Thr at position 63. Thus, additional lesions that may affect the expression of viral genes and the quantity and nature of the putative c-myc gene product occur in provirally mutated c-myc alleles and may contribute to tumor progression.
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PMID:Proviral deletions and oncogene base-substitutions in insertionally mutagenized c-myc alleles may contribute to the progression of avian bursal tumors. 632 73

Bisulfite mutagenesis techniques have been used to introduce single-point mutations within a region of the Rous sarcoma virus src gene defined by a BglI restriction endonuclease cleavage site. The mutants of Rous sarcoma virus that are produced by these techniques encode src proteins which contain single amino acid changes within a highly conserved amino acid sequence encompassing residues 430 to 433. DNA from the mutants CHpm26 ( Ala430 to Val), CHpm9 ( Pro431 to Ser), CHpm6 ( Glu432 to Lys), and CHpm65 ( Ala433 to Thr) each failed to transform chicken cells upon transfection, whereas DNA from CHpm59 (a third base alteration in the codon for Glu432 ) readily transformed chicken cells. Analysis of immune complexes containing the altered src proteins indicates that these proteins have decreased tyrosine protein kinase activity in vitro. In vivo labeling of cells infected with the mutant virus revealed diminished levels of the tyrosine-phosphorylated 34,000-molecular-weight protein. These data indicate that mutations within the sequence Ala430 - Pro431 - Glu432 - Ala433 lead to alterations in pp60src-specific tyrosine protein kinase activity and a concomitant loss of transforming potential of the mutant virus.
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PMID:Amino acid alterations within a highly conserved region of the Rous sarcoma virus src gene product pp60src inactivate tyrosine protein kinase activity. 632 73

cDNA clones encoding human apolipoprotein CII (apo CII) were identified by screening an adult human liver cDNA library with a mixed oligonucleotide probe corresponding to all possible codons for apo CII amino acid 6-10. One clone with an approximately equal to 500-base-pair (bp) insert, designated pCII -711, was selected for DNA sequence analysis. This clone contained a DNA sequence that corresponded with the previously reported amino acid sequence of apo CII with only minor differences. The DNA sequence specified a polypeptide of 79 amino acids, compared to the 78 amino acids previously reported. The pCII -711 clone contains a 36-bp DNA sequence upstream from that specifying the NH2-terminal threonine which, when read in frame, specifies the amino acid sequence Leu-Val-Leu-Leu-Val-Leu-Gly-Phe-Glu-Val-Gln-Gly and may be part of an apo CII signal peptide. The pCII -711 clone also contains a 144-bp region that corresponds to the 3' untranslated region of apo CII mRNA as well as a portion of the poly(A) tail. Clone pCII -711 was used to isolate and characterize by restriction endonuclease digestion the gene for apo CII from a human genomic library. In addition, through Southern blot analysis of DNA from human-rodent somatic cell hybrids, clone pCII -711 also was used to provisionally map the gene for apo CII to human chromosome 19.
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PMID:Isolation and sequence of a human apolipoprotein CII cDNA clone and its use to isolate and map to human chromosome 19 the gene for apolipoprotein CII. 632 78

Interleukin-6 (IL-6) is a multifunctional cytokine that plays an important role in host defense. It has been predicted that IL-6 may fold as a 4 alpha-helix bundle structure with up-up-down-down topology. Despite a high degree of sequence similarity (42%) the human and mouse IL-6 polypeptides display distinct species-specific activities. Although human IL-6 (hIL-6) is active in both human and mouse cell assays, mouse IL-6 (mIL-6) is not active on human cells. Previously, we demonstrated that the 5 C-terminal residues of mIL-6 are important for activity, conformation, and stability (Ward LD et al., 1993, Protein Sci 2:1472-1481). To further probe the structure-function relationship of this cytokine, we have constructed several human/mouse IL-6 hybrid molecules. Restriction endonuclease sites were introduced and used to ligate the human and mouse sequences at junction points situated at Leu-62 (Lys-65 in mIL-6) in the putative connecting loop AB between helices A and B, at Arg-113 (Val-117 in mIL-6) at the N-terminal end of helix C, at Lys-150 (Asp-152 in mIL-6) in the connecting loop CD between helices C and D, and at Leu-178 (Thr-180 in mIL-6) in helix D. Hybrid molecules consisting of various combinations of these fragments were constructed, expressed, and purified to homogeneity. The conformational integrity of the IL-6 hybrids was assessed by far-UV CD. Analysis of their biological activity in a human bioassay (using the HepG2 cell line), a mouse bioassay (using the 7TD1 cell line), and receptor binding properties indicates that at least 2 regions of hIL-6, residues 178-184 in helix D and residues 63-113 in the region incorporating part of the putative connecting loop AB through to the beginning of helix C, are critical for efficient binding to the human IL-6 receptor. For human IL-6, it would appear that interactions between residues Ala-180, Leu-181, and Met-184 and residues in the N-terminal region may be critical for maintaining the structure of the molecule; replacement of these residues with the corresponding 3 residues in mouse IL-6 correlated with a significant loss of alpha-helical content and a 200-fold reduction in activity in the mouse bioassay. A homology model of mIL-6 based on the X-ray structure of human granulocyte colony-stimulating factor is presented.
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PMID:Structure-function analysis of human IL-6: identification of two distinct regions that are important for receptor binding. 753 47

The RET proto-oncogene, a receptor tyrosine kinase, has been evaluated as a candidate gene for multiple endocrine neoplasia type 2A and type 2B (MEN 2A and MEN 2B), for familial medullary thyroid carcinoma (FMTC), and for sporadic cases of medullary thyroid carcinoma (MTC) and pheochromocytomas. We determined the genomic structure of RET and used single-strand conformational polymorphism (SSCP) analysis to identify sequence variants in genomic DNA from families segregating MEN 2 and FMTC. In addition, we examined paired tumour and lymphocyte genomic DNAs from individuals with sporadic cases of MTC and pheochromocytoma. Altogether, we and others found 21 missense mutations in five cysteines clustered in the extra-cellular domain of RET (exons 10 and 11) associated with 111 MEN 2A and FMTC families. In contrast, a single point mutation that results in the substitution of threonine for methionine within the catalytic core of the tyrosine kinase domain (codon 918, exon 16) is responsible for all 66 reported cases of MEN 2B. Two missense mutations and a six base-pair deletion were identified in MTC tumour DNA, but no mutations were identified from pheochromocytoma tumour DNAs. A predictive DNA test for MEN 2A-associated mutations in RET has been developed that is based on detection of missense mutations by polymerase chain reaction (PCR) amplification and restriction endonuclease cleavage. A dominant oncogene model for the action of the RET gene product is proposed as a mechanism of action in MEN 2A, MEN 2B, FMTC and for at least some cases of sporadic MTC.
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PMID:The RET proto-oncogene and cancer. 759 67


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