Guanidine Hydrochloride Exerts Dual Effects on the Tryptophan Synthase α2β2Complex as a Cation Activator and as a Modulator of the Active Site Conformation‡

Biochemistry ◽  
1999 ◽  
Vol 38 (24) ◽  
pp. 7881-7890 ◽  
Author(s):  
Ying-Xin Fan ◽  
Peter McPhie ◽  
Edith Wilson Miles
Keyword(s):  
Active Site ◽  
Guanidine Hydrochloride ◽  
Tryptophan Synthase ◽  
Active Site Conformation

Crystal structure of acetylxylan esterase from Caldanaerobacter subterraneus subsp. tengcongensis

2021 ◽  
Vol 77 (11) ◽  
Author(s):  
Kohei Sasamoto ◽  
Tomoki Himiyama ◽  
Kunihiko Moriyoshi ◽  
Takashi Ohmoto ◽  
Koichi Uegaki ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Cellulose Acetate ◽  
Electron Density ◽  
Active Site ◽  
Catalytic Domain ◽  
Crystal Packing ◽  
Signal Sequence ◽  
Industrial Applications ◽  
Side Chain ◽  
Active Site Conformation

The acetylxylan esterases (AXEs) classified into carbohydrate esterase family 4 (CE4) are metalloenzymes that catalyze the deacetylation of acetylated carbohydrates. AXE from Caldanaerobacter subterraneus subsp. tengcongensis (TTE0866), which belongs to CE4, is composed of three parts: a signal sequence (residues 1–22), an N-terminal region (NTR; residues 23–135) and a catalytic domain (residues 136–324). TTE0866 catalyzes the deacetylation of highly substituted cellulose acetate and is expected to be useful for industrial applications in the reuse of resources. In this study, the crystal structure of TTE0866 (residues 23–324) was successfully determined. The crystal diffracted to 1.9 Å resolution and belonged to space group I212121. The catalytic domain (residues 136–321) exhibited a (β/α)7-barrel topology. However, electron density was not observed for the NTR (residues 23–135). The crystal packing revealed the presence of an intermolecular space without observable electron density, indicating that the NTR occupies this space without a defined conformation or was truncated during the crystallization process. Although the active-site conformation of TTE0866 was found to be highly similar to those of other CE4 enzymes, the orientation of its Trp264 side chain near the active site was clearly distinct. The unique orientation of the Trp264 side chain formed a different-shaped cavity within TTE0866, which may contribute to its reactivity towards highly substituted cellulose acetate.

scholarly journals The structures of rnase a complexed with 3′-CMP and d(CpA): Active site conformation and conserved water molecules

1994 ◽  
Vol 3 (12) ◽  
pp. 2322-2339 ◽  
Author(s):  
Ingrid Zegers ◽  
Dominique Maes ◽  
Minh-Hoa Dao-Thi ◽  
Lode Wyns ◽  
Freddy Poortmans ◽  
...  
Keyword(s):  
Active Site ◽  
Rnase A ◽  
Water Molecules ◽  
Conserved Water Molecules ◽  
Active Site Conformation

Solution-State17O Quadrupole Central-Transition NMR Spectroscopy in the Active Site of Tryptophan Synthase

2015 ◽  
Vol 128 (4) ◽  
pp. 1372-1376 ◽  
Author(s):  
Robert P. Young ◽  
Bethany G. Caulkins ◽  
Dan Borchardt ◽  
Daryl N. Bulloch ◽  
Cynthia K. Larive ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Active Site ◽  
Tryptophan Synthase ◽  
Central Transition

scholarly journals Activation of chicken liver dihydrofolate reductase by urea and guanidine hydrochloride is accompanied by conformational change at the active site

1996 ◽  
Vol 315 (1) ◽  
pp. 97-102 ◽  
Author(s):  
Ying-xin FAN ◽  
Ming JU ◽  
Jun-mei ZHOU ◽  
Chen-lu TSOU
Keyword(s):  
Catalytic Activity ◽  
Dihydrofolate Reductase ◽  
Conformational Changes ◽  
Active Site ◽  
Guanidine Hydrochloride ◽  
Chicken Liver ◽  
Peptide Fragments ◽  
Enhanced Fluorescence ◽  
Compact Structure ◽  
Mouse Leukaemia

It has been reported that the activation of dihydrofolate reductase (DHFR) from L1210 mouse leukaemia cells by KCl or thiol modifiers is accompanied by increased digestibility by proteinases [Duffy, Beckman, Peterson, Vitols and Huennekens (1987) J. Biol. Chem. 262, 7028–7033], suggesting a loosening up of the general compact structure of the enzyme. In the present study, the peptide fragments liberated from the chicken liver enzyme by digestion with trypsin in dilute solutions of urea or guanidine hydrochloride (GuHCl) have been separated by FPLC and sequenced. The sequences obtained are unique when compared with the known sequence of DHFR and thus allow the points of proteolytic cleavage identified for the urea- and GuHCl-activated enzyme to be at or near the active site. It was also indicated by the enhanced fluorescence of 2-p-toluidinylnaphthalene 6-sulphonate that conformational changes at the active site in dilute GuHCl parallel GuHCl activation. The above results indicate that the activation of DHFR in dilute denaturants is accompanied by a loosening up of its compact structure especially at or near the active site, suggesting that the flexibility at its active site is essential for the full expression of its catalytic activity.

Quenching of Fluorescent Nucleotides Bound to Myosin: A Probe of the Active-Site Conformation

Biochemistry ◽  
1994 ◽  
Vol 33 (42) ◽  
pp. 12720-12728 ◽  
Author(s):  
Kathleen Franks-Skiba ◽  
Thomas Hwang ◽  
Roger Cooke
Keyword(s):  
Active Site ◽  
Fluorescent Nucleotides ◽  
Active Site Conformation
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