scholarly journals Amino acid substitutions in mutant forms of histidinol dehydrogenase from Neurospora crassa

1967 ◽  
Vol 105 (1) ◽  
pp. 39-44 ◽  
Author(s):  
D J Bennett ◽  
E H Creaser
Keyword(s):  
Amino Acid ◽  
Neurospora Crassa ◽  
Temperature Sensitive ◽  
Amino Acid Substitutions ◽  
Wild Type ◽  
Temperature Sensitive Mutants ◽  
Nad Oxidoreductase ◽  
Histidinol Dehydrogenase ◽  
Mutant Forms ◽  
Two Temperature

Amino acid changes in the enzyme l-histidinol dehydrogenase (l-histidinol–NAD oxidoreductase, EC 1.1.1.23) have been determined between the wild-type Neurospora crassa and two temperature-sensitive mutants. Comparison was made between amino acid analyses of peptides of differing electrophoretic and chromatographic mobilities resulting from tryptic and chymotryptic digestion of protein from wild-type and mutant K26, and wild-type and mutant K445 strains, respectively. The analyses demonstrate the substitution of aspartic acid for alanine in mutant K26, and leucine for histidine in mutant K445. The effects of the resulting changes in polarity and charge are discussed in relation to the catalytic functioning of the proteins.

STUDIES ON BIOSYNTHETIC ENZYMES: I. MUTANT FORMS OF HISTIDINOL DEHYDROGENASE FROM NEUROSPORA CRASSA

1965 ◽  
Vol 43 (7) ◽  
pp. 993-1000 ◽  
Author(s):  
E. H. Creaser ◽  
D. J. Bennett ◽  
R. B. Drysdale
Keyword(s):  
Activation Energy ◽  
Neurospora Crassa ◽  
Kinetic Properties ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Temperature Sensitive Mutants ◽  
Michaelis Constants ◽  
Histidinol Dehydrogenase ◽  
Mutant Forms ◽  
Two Temperature

Data are presented on the kinetic properties of the enzyme histidinol dehydrogenase obtained from the wild type Neurospora crassa and from 15 mutants. Differences were observed in pH curves and in Michaelis constants, both for histidinol and NAD. Ten mutants had modified affinity for NAD and three for histidinol, and one was modified in both these parameters. Two temperature-sensitive mutants were found to have an enzyme with a different activation energy from the normal. The data are discussed in relation to theories about whether histidinol dehydrogenase is a multifunctional enzyme in this organism or is part of an operon system.

scholarly journals Altering Catalytic Properties of 3-Chlorocatechol-Oxidizing Extradiol Dioxygenase fromSphingomonas xenophaga BN6 by Random Mutagenesis

2001 ◽  
Vol 183 (7) ◽  
pp. 2322-2330 ◽  
Author(s):  
Ulrich Riegert ◽  
Sibylle Bürger ◽  
Andreas Stolz
Keyword(s):  
Amino Acid ◽  
Random Mutagenesis ◽  
Ring Cleavage ◽  
Amino Acid Substitutions ◽  
The Novel ◽  
Wild Type ◽  
Wild Type Enzyme ◽  
Extradiol Dioxygenase ◽  
Mutant Forms ◽  
Sphingomonas Xenophaga

ABSTRACT The 2,3-dihydroxybiphenyl 1,2-dioxygenase from Sphingomonas xenophaga strain BN6 (BphC1) oxidizes 3-chlorocatechol by a rather unique distal ring cleavage mechanism. In an effort to improve the efficiency of this reaction, bphC1 was randomly mutated by error-prone PCR. Mutants which showed increased activities for 3-chlorocatechol were obtained, and the mutant forms of the enzyme were shown to contain two or three amino acid substitutions. Variant enzymes containing single substitutions were constructed, and the amino acid substitutions responsible for altered enzyme properties were identified. One variant enzyme, which contained an exchanged amino acid in the C-terminal part, revealed a higher level of stability during conversion of 3-chlorocatechol than the wild-type enzyme. Two other variant enzymes contained amino acid substitutions in a region of the enzyme that is considered to be involved in substrate binding. These two variant enzymes exhibited a significantly altered substrate specificity and an about fivefold-higher reaction rate for 3-chlorocatechol conversion than the wild-type enzyme. Furthermore, these variant enzymes showed the novel capability to oxidize 3-methylcatechol and 2,3-dihydroxybiphenyl by a distal cleavage mechanism.

Recombinant Variants of Tissue-Type Plasminogen Activator Containing Amino Acid Substitutions in the Finger Domain

1992 ◽  
Vol 68 (06) ◽  
pp. 672-677 ◽  
Author(s):  
Hitoshi Yahara ◽  
Keiji Matsumoto ◽  
Hiroyuki Maruyama ◽  
Tetsuya Nagaoka ◽  
Yasuhiro Ikenaka ◽  
...  
Keyword(s):  
Amino Acid ◽  
Plasminogen Activator ◽  
Half Life ◽  
Tissue Type ◽  
Clot Lysis ◽  
Amino Acid Substitutions ◽  
Wild Type ◽  
Plasma Clot ◽  
Tissue Type Plasminogen Activator ◽  
Type Plasminogen Activator

SummaryTissue-type plasminogen activator (t-PA) is a fibrin-specific agent which has been used to treat acute myocardial infarction. In an attempt to clarify the determinants for its rapid clearance in vivo and high affinity for fibrin clots, we produced five variants containing amino acid substitutions in the finger domain, at amino acid residues 7–9, 10–14, 15–19, 28–33, and 37–42. All the variants had a prolonged half-life and a decreased affinity for fibrin of various degrees. The 37–42 variant demonstrated about a 6-fold longer half-life with a lower affinity for fibrin. Human plasma clot lysis assay estimated the fibrinolytic activity of the 37–42 variant to be 1.4-fold less effective than that of the wild-type rt-PA. In a rabbit jugular vein clot lysis model, doses of 1.0 and 0.15 mg/kg were required for about 70% lysis in the wild-type and 37–42 variant, respectively. Fibrinogen was degraded only when the wild-type rt-PA was administered at a dose of 1.0 mg/kg. These findings suggest that the 37–42 variant can be employed at a lower dosage and that it is a more fibrin-specific thrombolytic agent than the wild-type rt-PA.

scholarly journals A Single Point Mutation, Asn16→Lys, Dictates the Temperature-Sensitivity of the Reovirus tsG453 Mutant

Viruses ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 289
Author(s):  
Kathleen K. M. Glover ◽  
Danica M. Sutherland ◽  
Terence S. Dermody ◽  
Kevin M. Coombs
Keyword(s):  
Amino Acid ◽  
Temperature Sensitivity ◽  
Reverse Genetics ◽  
Core Protein ◽  
Single Point ◽  
Single Amino Acid ◽  
Single Point Mutation ◽  
Temperature Sensitive ◽  
Amino Acid Substitutions ◽  
Gene Encoding

Studies of conditionally lethal mutants can help delineate the structure-function relationships of biomolecules. Temperature-sensitive (ts) mammalian reovirus (MRV) mutants were isolated and characterized many years ago. Two of the most well-defined MRV ts mutants are tsC447, which contains mutations in the S2 gene encoding viral core protein σ2, and tsG453, which contains mutations in the S4 gene encoding major outer-capsid protein σ3. Because many MRV ts mutants, including both tsC447 and tsG453, encode multiple amino acid substitutions, the specific amino acid substitutions responsible for the ts phenotype are unknown. We used reverse genetics to recover recombinant reoviruses containing the single amino acid polymorphisms present in ts mutants tsC447 and tsG453 and assessed the recombinant viruses for temperature-sensitivity by efficiency-of-plating assays. Of the three amino acid substitutions in the tsG453 S4 gene, Asn16-Lys was solely responsible for the tsG453ts phenotype. Additionally, the mutant tsC447 Ala188-Val mutation did not induce a temperature-sensitive phenotype. This study is the first to employ reverse genetics to identify the dominant amino acid substitutions responsible for the tsC447 and tsG453 mutations and relate these substitutions to respective phenotypes. Further studies of other MRV ts mutants are warranted to define the sequence polymorphisms responsible for temperature sensitivity.

scholarly journals Role of SpoVA Proteins in Release of Dipicolinic Acid during Germination of Bacillus subtilis Spores Triggered by Dodecylamine or Lysozyme

2006 ◽  
Vol 189 (5) ◽  
pp. 1565-1572 ◽  
Author(s):  
Venkata Ramana Vepachedu ◽  
Peter Setlow
Keyword(s):  
Bacillus Subtilis ◽  
Small Molecules ◽  
Spore Germination ◽  
Dipicolinic Acid ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Ph Optimum ◽  
Inner Membrane ◽  
Temperature Sensitive Mutants

ABSTRACT The release of dipicolinic acid (DPA) during the germination of Bacillus subtilis spores by the cationic surfactant dodecylamine exhibited a pH optimum of ∼9 and a temperature optimum of 60°C. DPA release during dodecylamine germination of B. subtilis spores with fourfold-elevated levels of the SpoVA proteins that have been suggested to be involved in the release of DPA during nutrient germination was about fourfold faster than DPA release during dodecylamine germination of wild-type spores and was inhibited by HgCl2. Spores carrying temperature-sensitive mutants in the spoVA operon were also temperature sensitive in DPA release during dodecylamine germination as well as in lysozyme germination of decoated spores. In addition to DPA, dodecylamine triggered the release of amounts of Ca2+ almost equivalent to those of DPA, and at least one other abundant spore small molecule, glutamic acid, was released in parallel with Ca2+ and DPA. These data indicate that (i) dodecylamine triggers spore germination by opening a channel in the inner membrane for Ca2+-DPA and other small molecules, (ii) this channel is composed at least in part of proteins, and (iii) SpoVA proteins are involved in the release of Ca2+-DPA and other small molecules during spore germination, perhaps by being a part of a channel in the spore's inner membrane.

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