Conformational changes and subunit communication in tryptophan synthase: effect of substrates and substrate analogs

Biochemistry ◽  
1992 ◽  
Vol 31 (33) ◽  
pp. 7535-7542 ◽  
Author(s):  
Giovanni B. Strambini ◽  
Patrizia Cioni ◽  
Alessio Peracchi ◽  
Andrea Mozzarelli
Keyword(s):  
Conformational Changes ◽  
Tryptophan Synthase ◽  
Substrate Analogs ◽  
Subunit Communication

Synergistic Regulation and Ligand-Induced Conformational Changes of Tryptophan Synthase

Biochemistry ◽  
2009 ◽  
Vol 48 (41) ◽  
pp. 9921-9931 ◽  
Author(s):  
M. Qaiser Fatmi ◽  
Rizi Ai ◽  
Chia-en A. Chang
Keyword(s):  
Conformational Changes ◽  
Tryptophan Synthase ◽  
Synergistic Regulation

Role of Met-542 as a guide for the conformational changes of Phe-601 that occur during the reaction of β-galactosidase (Escherichia coli)

2010 ◽  
Vol 88 (5) ◽  
pp. 861-869 ◽  
Author(s):  
Megan L. Dugdale ◽  
Dayna L. Dymianiw ◽  
Bhawanjot K. Minhas ◽  
Igor D’Angelo ◽  
Reuben E. Huber
Keyword(s):  
Energy Level ◽  
Transition State ◽  
Conformational Changes ◽  
Open Loop ◽  
Side Chain ◽  
Transition State Analog ◽  
Substrate Analogs ◽  
Transition State Analogs ◽  
Substrate Analog

The Met-542 residue of β-galactosidase is important for the enzyme’s activity because it acts as a guide for the movement of the benzyl side chain of Phe-601 between two stable positions. This movement occurs in concert with an important conformational change (open vs. closed) of an active site loop (residues 794–803). Phe-601 and Arg-599, which interact with each other via the π electrons of Phe-601 and the guanidium cation of Arg-599, move out of their normal positions and become disordered when Met-542 is replaced by an Ala residue because of the loss of the guide. Since the backbone carbonyl of Phe-601 is a ligand for Na+, the Na+ also moves out of its normal position and becomes disordered; the Na+ binds about 120 times more poorly. In turn, two other Na+ ligands, Asn-604 and Asp-201, become disordered. A substrate analog (IPTG) restored Arg-599, Phe-601, and Na+ to their normal open-loop positions, whereas a transition state analog (d-galactonolactone) restored them to their normal closed-loop positions. These compounds also restored order to Phe-601, Asn-604, Asp-201, and Na+. Binding energy was, however, necessary to restore structure and order. The Ks values of oNPG and pNPG and the competitive Ki values of substrate analogs were 90–250 times higher than with native enzyme, whereas the competitive Ki values of transition state analogs were ~3.5–10 times higher. Because of this, the E•S energy level is raised more than the E•transition state energy level and less activation energy is needed for galactosylation. The galactosylation rates (k2) of M542A–β-galactosidase therefore increase. However, the rate of degalactosylation (k3) decreased because the E•transition state complex is less stable.

Conformational Changes in the α-Subunit Coupled to Binding of the β2-Subunit of Tryptophan Synthase fromEscherichia coli:  Crystal Structure of the Tryptophan Synthase α-Subunit Alone†,‡

Biochemistry ◽  
2005 ◽  
Vol 44 (4) ◽  
pp. 1184-1192 ◽  
Author(s):  
Kazuya Nishio ◽  
Yukio Morimoto ◽  
Manabu Ishizuka ◽  
Kyoko Ogasahara ◽  
Tomitake Tsukihara ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Conformational Changes ◽  
Tryptophan Synthase ◽  
Α Subunit ◽  
Fromescherichia Coli

Large conformational changes in the Escherichia coli tryptophan synthase β2 subunit upon pyridoxal 5′-phosphate binding

FEBS Journal ◽  
2010 ◽  
Vol 277 (9) ◽  
pp. 2157-2170 ◽  
Author(s):  
Kazuya Nishio ◽  
Kyoko Ogasahara ◽  
Yukio Morimoto ◽  
Tomitake Tsukihara ◽  
Soo Jae Lee ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Conformational Changes ◽  
Tryptophan Synthase ◽  
Phosphate Binding

Crystal Structures of a Mutant (βK87T) Tryptophan Synthase α2β2Complex with Ligands Bound to the Active Sites of the α- and β-Subunits Reveal Ligand-Induced Conformational Changes‡

Biochemistry ◽  
1997 ◽  
Vol 36 (25) ◽  
pp. 7664-7680 ◽  
Author(s):  
Sangkee Rhee ◽  
Kevin D. Parris ◽  
C. Craig Hyde ◽  
S. Ashraf Ahmed ◽  
Edith Wilson Miles ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Conformational Changes ◽  
Active Sites ◽  
Tryptophan Synthase ◽  
Α And Β Subunits
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