Histidine Requirement Research Articles

Relaxed rrn expression and amino acid requirement of a Corynebacterium glutamicum rel mutant defective in (p)ppGpp metabolism

The stringent response in Corynebacterium glutamicum was investigated. Sets of rrn– cat fusions were constructed in their native chromosomal position to examine the effects of amino acid starvation in a rel + strain and a Δ rel mutant defective in (p)ppGpp metabolism. The expression of the six rrn operons in the rel + control was stringently regulated and reduced to 79% upon induction of amino acid starvation. The Δ rel mutant displayed a relaxed regulation and was unable to reduce the rrn expression under amino acid depletion conditions. In addition, the Δ rel mutant grew more slowly in minimal medium than a rel + control. This growth effect was restored by a plasmid-encoded copy of rel or, alternatively, by supplementation of the minimal medium with the amino acid mixture casamino acids. In particular, the Δ rel strain of C. glutamicum displayed a requirement for the amino acids histidine and serine.

Relaxedrrnexpression and amino acid requirement of aCorynebacterium glutamicum relmutant defective in (p)ppGpp metabolism

The stringent response in Corynebacterium glutamicum was investigated. Sets of rrn-cat fusions were constructed in their native chromosomal position to examine the effects of amino acid starvation in a rel(+) strain and a Deltarel mutant defective in (p)ppGpp metabolism. The expression of the six rrn operons in the rel(+) control was stringently regulated and reduced to 79% upon induction of amino acid starvation. The Deltarel mutant displayed a relaxed regulation and was unable to reduce the rrn expression under amino acid depletion conditions. In addition, the Deltarel mutant grew more slowly in minimal medium than a rel(+) control. This growth effect was restored by a plasmid-encoded copy of rel or, alternatively, by supplementation of the minimal medium with the amino acid mixture casamino acids. In particular, the Deltarel strain of C. glutamicum displayed a requirement for the amino acids histidine and serine.

Catalytic center of an archaeal type 2 ribonuclease H as revealed by X-ray crystallographic and mutational analyses.

The catalytic center of an archaeal Type 2 RNase H has been identified by a combination of X-ray crystallographic and mutational analyses. The crystal structure of the Type 2 RNase H from Thermococcus kodakaraensis KOD1 has revealed that the N-terminal major domain adopts the RNase H fold, despite the poor sequence similarity to the Type 1 RNase H. Mutational analyses showed that the catalytic reaction requires four acidic residues, which are well conserved in the Type 1 RNase H and the members of the polynucleotidyl transferase family. Thus, the Type 1 and Type 2 RNases H seem to share a common catalytic mechanism, except for the requirement of histidine as a general base in the former enzyme. Combined with the results from deletion mutant analyses, the structure suggests that the C-terminal domain of the Type 2 RNase H is involved in the interaction with the DNA/RNA hybrid.

Elastase substrate specificity tailored through substrate-assisted catalysis and phage display.

The catalytic histidine of human neutrophil elastase was replaced with alanine (H57A) to determine if a substrate histidine could substitute for the missing catalytic group-'substrate-assisted catalysis'. H57A and wild-type elastase were recovered directly from Pichia pastoris following expression from a synthetic gene lacking the elastase pro sequence, thereby obviating the need for zymogen activation. Potential histidine-containing substrates for H57A elastase were identified from a phage library of randomized sequences. One such sequence, REHVVY, was cleaved by H57A elastase with a catalytic efficiency, k(cat)/K(M), of 2800 s(-1) M(-1), that is within 160-fold of wild-type elastase. In contrast, wild-type but not H57A elastase cleaved the related non-histidine containing sequence, REAVVY. Ten different histidine-containing linkers were cleaved by H57A elastase. In addition to the requirement for a P2 histidine, significant preferences were observed at other subsites including valine or threonine at P1, and methionine or arginine at P4. A designed sequence, MEHVVY, containing the preferred residues identified at each subsite proved to be a more favorable substrate than any of the phage-derived sequences. Extension of substrate-assisted catalysis to elastase suggests that this engineering strategy may be widely applicable to other serine proteases thereby creating a family of highly specific histidine-dependant proteases.

Histidine placement in de novo-designed heme proteins.

The effects of histidine residue placement in a de novo-designed four-alpha-helix bundle are investigated by placement of histidine residues at coiled coil heptad a positions in two distinct heptads and at each position within a single heptad repeat of our prototype heme protein maquette, [H10H24]2 [[Ac-CGGGELWKL x HEELLKK x FEELLKL x HEERLKK x L-CONH2]2]2 composed of a generic (alpha-SS-alpha)2 peptide architecture. The heme to peptide stoichiometry of variants of [H10H24]2 with either or both histidines on each helix replaced with noncoordinating alanine residues ([H10A24]2, [A10H24]2, and [A10A24]2) demonstrates the obligate requirement of histidine for biologically significant heme affinity. Variants of [A10A24]2, [[Ac-CGGGELWKL x AEELLKK x FEELLKL x AEERLKK x L-CONH2]2]2, containing a single histidine per helix in positions 9 to 15 were evaluated to verify the design based on molecular modeling. The bis-histidine site formed between heptad positions a at 10 and 10' bound ferric hemes with the highest affinity, Kd1 and Kd2 values of 1.5 and 800 nM, respectively. Placement of histidine at position 11 (heptad position b) resulted in a protein that bound a single heme with moderate affinity, Kd1 of 9.5 microM, whereas the other peptides had no measurable apparent affinity for ferric heme with Kd1 values >200 microM. The bis-histidine ligation of heme to [H10A24]2 and [H11A24]2 was confirmed by electron paramagnetic resonance spectroscopy. The protein design rules derived from this study, together with the narrow tolerances revealed, are applicable for improving future heme protein designs, for analyzing the results of randomized heme protein combinatorial libraries, as well as for implementation in automated protein design.

Potassium Transport by Amino Acid Permeases in Saccharomyces cerevisiae

Deletion of the potassium transporter genes TRK1 and TRK2 impairs potassium uptake in Saccharomyces cerevisiae, resulting in a greatly increased requirement for the ion and the inability to grow on low pH medium. Selection for mutations that restored growth of trk1Delta trk2Delta cells on low pH (3.0) medium led to the isolation of a dominant suppressor that also partially suppressed the increased K+ requirement of these cells. Molecular analysis revealed the suppressor to be an allele of BAP2 that encodes a permease for branched chain amino acids. The suppressor mutation (BAP2-1) converts a phenylalanine codon, highly conserved among the amino acid permease genes, to a serine codon in a region predicted to lie within the sixth membrane-spanning domain. Generation of the analogous mutation in the histidine permease produced an allele, HIP1-293, that similarly suppressed the low pH sensitivity of trk1Delta trk2Delta cells. Suppression of trk1Delta trk2Delta phenotypes by BAP2-1 or HIP1-293 was correlated with increased Rb+ uptake. The presence of the substrate amino acids enhanced but was not essential for suppression of trk1Delta trk2Delta phenotypes and increased Rb+ uptake. The conserved site altered by the suppressor mutations appears to be important; his4 HIP1-293 cells show an increased requirement for histidine compared with his4 HIP1 cells.

Arginine and histidine requirements of the Indian major carp, Labeo rohita (Hamilton)

Growth studies were conducted to quantify requirements for the essential amino acids (EAA), arginine and histidine in Labeo rohita (Hamilton). Diets incorporating casein and gelatine, as sources of intact protein, supplemented with crystalline amino acids were formulated to a crude protein content of 400 g kg−1. Diets with six graded levels of arginine (14.6, 17.0, 19.0, 21.0, 23.0 and 25 g kg−1) and histidine (3.2, 5.0, 7.0, 9.0, 11.0 and 13.0 g kg−1) were formulated and fed to triplicate groups of juvenile rohu twice a day up to satiation for 60 days. Dietary requirements for arginine and histidine for rohu, estimated using break point analysis, were 23 and 9 of the diet respectively (57.5 and 22.5 g kg−1 of dietary protein). Food conversion rate, specific growth rate and survival were better in treatments with diets containing optimum levels of EAA.

Chemical modification of glucosamine-6-phosphate synthase by diethyl pyrocarbonate: Evidence of histidine requirement for enzymatic activity

Glucosamine-6-phosphate synthase from Escherichia coli was inactivated by diethylpyrocarbonate at pH 7.3 and 4 °C with a second-order rate constant of 1220 m −1 min −1. The difference spectrum of inactivated vs native enzyme had a maximum absorption at 242 nm, which is characteristic of N-carbethoxyhistidine. No trough at around 280 nm due to O-carbethoxytyrosine was observed and the sulfhydryl content of the enzyme was unchanged. Studies with [ 14C]diethylpyrocarbonate provided evidence that derivatization of a single histidine residue of the amino-terminal glutamine-binding domain inactivated glucosamine-6P synthase. These results are consistent with the participation of an histidine residue in a catalytic triad, Cys/His/Asp, necessary to generate ammonia from glutamine.

Apportioning histidine requirements for maintenance versus growth

Purified diets containing six levels of histidine were fed to growing rats to evaluate histidine requirements for growth and for maintenance. A model was developed to subdivide the requirement for maintenance from the requirement for growth. Based on weight gain response, the histidine need for growth was 4.02 mg/g weight gain and the daily histidine need for maintenance was .130 times metabolic body size (Wg .75). Based on nitrogen gain response, the histidine need for growth was .168 mg/mg N gain and the daily histidine need for maintenance (mg) was .137 times metabolic body size (Wg .75). The plateau of plasma histidine concentration was reached at 22 mg intake/day. Previous histidine requirements for growth (for less than 5 g daily weight gain or 120 mg daily N retention) and for maintenance were in very close agreement with these estimates. As a percentage of retained protein, according to theses equations, histidine was calculated to be 2.7%; the reported histidine content of rat muscle CP is 2.85%.

Histidine and Tryptophan Requirement of Growing Chicks

Experiments were conducted to determine the His and Trp requirement of broiler chicks during the period 8 to 22 days posthatching. A His- or Trp-deficient diet (.32% total His; .18% total Trp; 25% CP; 3,200 kcal MEn/kg) based upon corn, feather meal, and soybean meal was supplemented with graded increments of either L-His-HCl·H2 O or L-Trp to produce growth responses. Growth rate and feed efficiency of birds fed the fully fortified experimental diet were similar to those of birds fed a corn and soybean meal positive control diet (23% CP; 3,200 kcal MEn/kg). True digestibility of the protein blend (corn, feather meal, and soybean meal) used in the basal diet was 81.4% for His and 83.3% for Trp as established in precision-fed, cecectomized adult cockerels. Requirements for digestible His and Trp were determined to be not greater than .31% (1.24% of CP) and .20% (.80% of CP), respectively, for maximal weight gain and feed efficiency. Translating the requirement estimates to practice, wherein a 23% corn and soybean meal diet would be fed, results in a total His requirement of .32% and a total Trp requirement of .22% of the diet during the broiler chick's 2nd and 3rd wk of life.

Contribution to our knowledge ofTrichophyton megninii

In addition to its requirement for histidine, Trichophyton megninii can be readily differentiated from certain other dermatophytes, particularly Trichophyton rubrum, by its "+" mating type and a positive urease test on urea-indole broth.

The amino acid and fatty acid compositions of selected tissues of the dolphin fish ( Coryphaena hippurus) and their nutritional implications

The amino acid and fatty acid compositions of muscle, gill, intestine, liver, ovaries, and whole bodies from captive juvenile and adult, and wild adult dolphin fish ( Coryphaena hippurus) were determined. Essential amino acid ratios ( A E ratios) of the whole body and individual tissues were calculated and compared. In addition, the concept of a metabolic A E ratio calculated from known daily protein turnover rates and from the amino acid profiles is introduced. Fatty acid profiles of phospholipid (PL) and triglyceride (TG) fractions in muscle and liver were also compared. There were few differences in the amino acid and fatty acid profiles of tissues between the different groups of dolphin fish examined. Linolenic series fatty acids were quantitatively the most important polyunsaturates in tissue PL fractions. C22: 6 n−3 was the major polyunsaturate present, accounting for approximately 20% of the total PLs in muscle and liver. There was no significant difference in tissue essential amino acid patterns between adult fish raised in captivity, and adult fish caught in the wild. However, the muscle of juvenile fish was lower in arginine and histidine contents than the muscle of adult fish. Ovaries had the lowest arginine, histidine, and tryptophan contents of all tissues measured. Calculated A E ratios of the muscle and whole body, and A E ratios based on the metabolic rates for protein turnover in muscle, gill, and intestine, were similar. All ratios predicted an ontological increase in dietary arginine, histidine, and tryptophan needs of dolphin fish consistent with the changes noted in tissue amino acid contents. It is concluded that the calculated A E ratios and fatty acid profiles of dolphin fish tissues may be useful guides in formulating diets for the culture of this species. The results obtained suggest that the requirements for arginine, histidine, and tryptophan may differ between subadult and adult fish. Dietary needs for linolenic series HUFAs, especially C22:6 n−3, are likely high throughout the life of this fish.

Isolation and Characterization of Mutants of Propionibacterium Strains

Procedures were developed to isolate and characterize mutants of strains of dairy propionibacteria. These procedures included the construction of minimal defined media to support growth of the strains, optimization of conditions of exposure of the strains to nitrosoguanidine, and identification of the phenotypes of the mutants that were generated. The minimal defined medium contained inorganic salts, adenosine, three vitamins, and sodium lactate as the carbon source, with cysteine, methionine, or cysteine plus methionine added as required by some strains. For mutagenesis, cells were exposed to either 100, 200, or 1000μg/ml nitrosoguanidine, depending on the sensitivity of the strain, for 60min at 35°C. At least nine stable mutants were isolated and characterized for each of the five strains under study. The most frequent mutations generated were requirements for arginine, histidine, methionine, and uracil and alteration in pigment production.

Histidine requirement of the young pig.

A histidine (HIS)-deficient, feather meal-corn-dried whey basal diet (19% protein and 3,200 Kcal ME/kg), supplemented with lysine, methionine and tryptophan, was employed to determine the HIS requirement of the growing pig between 10 and 20 kg live weight. Using a chick bioavailability growth assay, the HIS-deficient basal diet was found to contain .19% bioavailable HIS. A preliminary pig study established that the HIS-deficient basal diet was capable of supporting good growth of pigs when supplemented with sufficient L-HIS.HCl.H2O. In the second pig experiment, crossbred pigs with an average initial weight of 10 kg were kept in individual metabolism crates and were fed to appetite in two feedings the HIS-deficient basal diet supplemented with 0, .06, .12 or .18% L-HIS. Rate and efficiency of weight gain increased linearly between 0 and .12% supplemental HIS, but the highest supplemental level of HIS did not improve performance further. Plasma HIS increased, whereas plasma urea-N remained unchanged, as the level of dietary HIS increased. The third pig experiment employed narrower increments of .06, .09 or .12% supplemental HIS, and a linear response in both gain and feed efficiency occurred. Viewing all experiments together, the bioavailable HIS requirement of the 10- to 20-kg pig was .31% of the diet. Assuming an 85% bioavailability of HIS in commercial diets based on corn and soybean meal, the total HIS level needed in practice would be .36%.

Histidine requirement of kittens for growth, haematopoiesis and prevention of cataracts.

1. The histidine requirement of growing kittens was determined from an experiment in which forty-eight kittens were randomly allocated to six amino acid-based diets supplying: 1.0, 1.5, 2.0, 2.5, 3.0 or 4.5 g histidine base/kg diet. 2. By 48 d it was obvious that 1.0 and 1.5 g histidine/kg diet were grossly inadequate so the kittens receiving these two diets were removed from the experiment. The other four groups of kittens continued to receive their diets for a total of 128 d. 3. Mean daily weight gain, nitrogen retention and food intake attained plateau values at 2.1 g histidine/kg diet. 4. Blood samples taken at 25 and 48 d after kittens were given the diets showed a significant effect of dietary histidine on haemoglobin (Hb) concentration. Hb and packed cell volume (PCV) attained asymptotic values at 3.0 g histidine/kg diet at 48 d. At 128 d, kittens consuming diets containing 2.0-4.5 g histidine/kg had similar Hb and PCV values. 5. Cataracts of both eyes were observed in two of nine female kittens which had received diets containing either 2.0 or 2.5 g histidine/kg. 6. A concentration of 3 g histidine/kg diet is recommended as a practical guide for feeding kittens. 7. There was a rectilinear relation (r2 0.99) between the logarithm of the histidine concentration of plasma and the concentration of histidine in the diet over the range 1.5-3.0 g histidine/kg diet.

Genetic transformation in the methanogen Methanococcus voltae PS.

Mutations causing requirements for histidine, purine, and vitamin B12 were obtained in strain PS of Methanococcus voltae (archaebacteria) upon irradiation with UV or gamma rays. The first two mutations were shown to revert at low frequencies and were used to demonstrate the occurrence of transformation with homologous, wild-type DNA. The transformation rates obtained for these presumably chromosomal markers were in the range of 2 to 100 transformants per microgram of DNA. Mutants resistant to 2-bromoethanesulfonate and to 5-methyl-DL-tryptophan were also isolated.

Effect of inhabitation by rumen protozoa on the nutritive value of protein in rumen contents.

Received December 22, 1986 The nutritive values of protein, expressed as a modified chemical score, in two kinds of rations were compared with those of the rumen contents of faunated and defaunated goats given the two rations singly. The first, second and third limiting amino acids in the rations were lysine, methionine and histidine, respectively. In the case of the rumen contents of faunated animals, histidine and methionine tended to be the first and second limiting amino acids, respectively, whereas in those of defaunated animals lysine tended to be the second limiting amino acid. The improvement in the quality of protein in the rations in the rumen and the strict requirement of histidine for ruminants were discussed.

Mise en évidence in vitro de la biosynthèse d'histamine à partir de carnosine par le rein de souris gravide

Kidneys of pregnant mice synthesize histamine when incubated in the presence of carnosine, manganese, and pyridoxal phosphate. Intensity of biosynthesis increases linearly with the amount of enzyme and the incubation time. The reaction can only be catalysed by two enzymes that are located in kidneys and act in succession: carnosinase, which hydrolyzes carnosine into its two moieties, and histidine decarboxylase, which transforms histidine, a product of carnosine degradation, into histamine. The biosynthesis of histamine from carnosine seems to increase with the progress of pregnancy. In nonpregnant mice, kidneys do not effect this biosynthesis. The above results directly demonstrate that carnosine may be used for histamine synthesis when the activity of histidine decarboxylase is high, as in pregnant mouse kidney. Vertebrate carnosine, its role still enigmatic, might thus be mainly a potential histidine reservoir that would be mobilized any time there is a significant requirement for histidine, such as for histamine biosynthesis.

Chemical modification of Escherichia coli RNA polymerase by diethyl pyrocarbonate: evidence of histidine requirement for enzyme activity and intrinsic zinc binding.

RNA polymerase (RPase) from Escherichia coli contains five subunits (alpha 2 beta beta' sigma) and two intrinsic Zn ions located in the beta and beta' subunits. This enzyme was rapidly inactivated by diethyl pyrocarbonate (DEP) at pH 6.0 and 25 degrees C. The difference spectrum of the DEP-inactivated and native RPases showed a single peak at 240 nm indicating the formation of N-carbethoxyhistidines. No decrease in absorbance at 278 nm, due to O-carbethoxytyrosine, or modification of amino and sulfhydryl groups was observed. Inactivated RPase with six to nine histidines being modified could be fully reactivated by incubation with 0.5 M hydroxylamine at pH 6.0 and room temperature for 1 h. No structural difference was detected between the native and modified enzymes as evidenced by UV/visible and fluorescence spectra, sodium dodecyl sulfate-polyacrylamide gel electrophoretic pattern, or gel filtration properties. Substrate ATP at 0.11 and 1.14 mM concentrations provided, respectively, 25% and 90% protection against DEP inactivation, while template DNA did not. These results suggest that one or more histidine residues is/are in close proximity to the substrate binding site. The pH dependence of the DEP inactivation of RPase suggested the modification of histidine at the active site with a pK value of 6.9. The inactivation of RPase by DEP and the formation of N-carbethoxyhistidine displayed a similar second-order rate constant of approximately 0.9 mM-1 min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Threonine, histidine and lysine requirements of chum salmon fry.

Three 4-week feeding studies were conducted to determine quantitative requirements of chumsalmon fry for threonine, histidine and lysine. The basal diet containing crystalline L-amino acids and 5% casein as nitrogen sources (40% crude protein) were isonitrogenously supplemented with graded level of threonine, histidine and lysine by adjusting the level of alanine. Based on growth data, the requirements for threonine, histidine and lysine were found out to be 1.2, 0.7 and 1.9 percent of diet (dry weight basis), or 3.0, 1.6 and 4.8 percent of dietary protein, respectively.