scholarly journals The effects of modification with N-bromosuccinimide on the binding of ligands to dihydrofolate reductase

1980 ◽  
Vol 187 (2) ◽  
pp. 501-506 ◽  
Author(s):  
J W Thomson ◽  
G C Roberts ◽  
A S Burgen
Keyword(s):  
Dihydrofolate Reductase ◽  
Lactobacillus Casei ◽  
Binding Constants ◽  
Coenzyme Binding ◽  
Spectrophotometric Methods ◽  
Substrate Analogues

The binding constants of substrate, inhibitors and coenzymes to native Lactobacillus casei dihydrofolate reductase and to the enzyme modified (at Trp-21) by N-bromosuccinimide have been determined using fluorimetric and spectrophotometric methods. The modification leads to only modest decreases (factors of 2-4) in the binding of substrate or substrate analogues, but the effects of coenzyme binding are much larger. The binding of NADPH is decreased by a factor of 200, but that of NADP+ by only a factor of 4, indicating a clear difference in their mode of interaction with the enzyme. The nature of this difference is discussed in the light of crystallographic and n.m.r. studies of the enzyme.

Effect of coenzyme binding on histidine residues of Lactobacillus casei dihydrofolate reductase

Biochemistry ◽  
1981 ◽  
Vol 20 (7) ◽  
pp. 1717-1722 ◽  
Author(s):  
Angela Gronenborn ◽  
Berry Birdsall ◽  
Eva I. Hyde ◽  
Gordon C. K. Roberts ◽  
James Feeney ◽  
...  
Keyword(s):  
Dihydrofolate Reductase ◽  
Lactobacillus Casei ◽  
Histidine Residues ◽  
Coenzyme Binding

scholarly journals Large-scale purification and characterization of dihydrofolate reductase from a methotrexate-resistant strain of Lactobacillus casei

1976 ◽  
Vol 157 (3) ◽  
pp. 559-571 ◽  
Author(s):  
J G Dann ◽  
G Ostler ◽  
R A Bjur ◽  
R W King ◽  
P Scudder ◽  
...  
Keyword(s):  
Dihydrofolate Reductase ◽  
Resistant Strain ◽  
Lactobacillus Casei ◽  
Large Scale ◽  
Gel Filtration ◽  
Deae Cellulose ◽  
Binding Constants ◽  
Affinity Column ◽  
Protein Fluorescence ◽  
Turnover Number

Dihydrofolate reductase has been purified from a methotrexate-resistant strain of Lactobacillus casei NCB 6375. By careful attention to growth conditions, up to 2.5 g of enzyme is obtained from a 400 litre culture. The purification procedure, involving poly-ethyleneimine treatment, DEAE-cellulose chromatography and affinity chromatography on methotrexate-aminohexyl-Sepharose, operates on the gram scale, with overall yields of 50-60%. Elution of the affinity column by reverse (upward) flow was used, as it led to recovery of the enzyme in a much smaller volume. The enzyme obtained appears to be more than 98% pure, as judged by gel electrophoresis, isoelectric focusing, and gel filtration. It has a mol.wt. of approx. 17900 and a turnover number of 4s-1 (50mM-triethanolamine/400mM-KCl, pH 7.2, 25 degrees C) with dihydrofolate and NADPH as substrates. The turnover number for folate is 0.02s-1. Michaelis constants for a variety of substrates have been measured by using a new fluorimetric assay (0.36 muM-dihydrofolate; 0.78 muM-NADPH), and binding constants determined by using the quenching of protein fluorescence (dihydrofolate, 2.25 X 10(6)M-1; NADPH, greater than 10(8)M-1). The pH/activity profile shows a single maximum at pH 7.3; at this pH, marked activation by 0.5M-NaCl is observed.

1 H nuclear magnetic resonance studies of the tyrosine residues of selectively deuterated Lactobacillus casei dihydrofolate reductase

1977 ◽  
Vol 196 (1124) ◽  
pp. 267-290 ◽  
Keyword(s):  
Chemical Shift ◽  
Ligand Binding ◽  
Dihydrofolate Reductase ◽  
Conformational Changes ◽  
Lactobacillus Casei ◽  
Inhibitor Binding ◽  
Tyrosine Residues ◽  
Coenzyme Binding ◽  
Binary Complexes ◽  
Significant Difference

A selectively deuterated dihydrofolate reductase, in which all the aro­matic protons except the 2, 6-protons of the tyrosine residues have been replaced by deuterium, has been prepared from Lactobacillus casei grown on a mixture of normal and deuterated amino acids. The aromatic region of the 1 H n. m. r. spectrum of this enzyme contains only resonances from the five tyrosine residues. For each tyrosine, the 2- and 6-protons have the same chemical shift, indicating rapid interconversion of the two conformers related by 180° rotation about the C β -C γ bond. The effects of sub­strate, inhibitor and coenzyme binding on the tyrosine residues have been investigated; four of the five residues are affected by ligand binding. Using the weakly binding ligands 2, 4-diaminopyrimidine and p -nitrobenzoyl-l-glutamate to connect the spectra of the free enzyme with those of the complexes, it is possible to give a detailed description of the effects of ligand binding on individual residues. In the binary complexes, methotrexate affects three tyrosine residues, only one of which is affected by folate, indicating a significant difference in the mode of binding of substrates and inhibitors. The co-enzymes NADP + and NADPH lead to broadly similar changes in the spectrum, except for one resonance which is shifted in opposite directions by the two co-enzymes. The oxidized and reduced co­enzymes also differ in their effects on the changes produced by inhibitor binding; the spectrum of the enzyme-NADPH-methotrexate complex is similar to that of the enzyme-methotrexate complex, while that of the enzyme-NADP + -methotrexate complex is not. In contrast to the be­haviour seen in the binary complexes, the spectrum of the enzyme-NADP + -folate complex is very similar to that of enzyme-NADP + -methotrexate. Evidence is presented that some, at least, of the changes in chemical shift of the tyrosine residues are due to ligand-induced conformational changes. The binding of p -nitrobenzoyl-l-glutamate to the enzyme-2, 4-diamino-pyrimidine complex is found to be tighter than that to the enzyme alone.

scholarly journals A 1H n.m.r. study of the role of the glutamate moiety in the binding of methotrexate to Lactobacillus casei dihydrofolate reductase

1984 ◽  
Vol 81 (2) ◽  
pp. 309-315 ◽  
Author(s):  
David J. Antonjuk ◽  
Berry Birdsall ◽  
H.T. Andrew Cheung ◽  
G. Marius Clore ◽  
James Feeney ◽  
...  
Keyword(s):  
Dihydrofolate Reductase ◽  
Lactobacillus Casei

Dihydrofolate reductase from amethopterin-resistant Lactobacillus casei

Biochemistry ◽  
1972 ◽  
Vol 11 (6) ◽  
pp. 1018-1023 ◽  
Author(s):  
L. E. Gundersen ◽  
R. B. Dunlap ◽  
N. G. L. Harding ◽  
J. H. Freisheim ◽  
F. Otting ◽  
...  
Keyword(s):  
Dihydrofolate Reductase ◽  
Lactobacillus Casei

Dihydrofolate reductase from amethopterin-resistant Lactobacillus casei

1977 ◽  
Vol 181 (2) ◽  
pp. 569-579 ◽  
Author(s):  
Taffy J. Williams ◽  
Timothy K. Lee ◽  
R.Bruce Dunlap
Keyword(s):  
Dihydrofolate Reductase ◽  
Lactobacillus Casei
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