Crystal Structures ofPasteurella multocidaSialyltransferase Complexes with Acceptor and Donor Analogues Reveal Substrate Binding Sites and Catalytic Mechanism†,‡

Biochemistry ◽  
2007 ◽  
Vol 46 (21) ◽  
pp. 6288-6298 ◽  
Author(s):  
Lisheng Ni ◽  
Harshal A. Chokhawala ◽  
Hongzhi Cao ◽  
Ryan Henning ◽  
Laura Ng ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Binding Sites ◽  
Catalytic Mechanism ◽  
Substrate Binding ◽  
Substrate Binding Sites

scholarly journals Structures of lipoyl synthase reveal a compact active site for controlling sequential sulfur insertion reactions

2014 ◽  
Vol 464 (1) ◽  
pp. 123-133 ◽  
Author(s):  
Jenny E. Harmer ◽  
Martyn J. Hiscox ◽  
Pedro C. Dinis ◽  
Stephen J. Fox ◽  
Andreas Iliopoulos ◽  
...  
Keyword(s):  
Crystal Structures ◽  
Active Site ◽  
Binding Sites ◽  
Substrate Binding ◽  
Insertion Reactions ◽  
Substrate Binding Sites ◽  
Lipoyl Synthase

The biosynthesis of lipoyl cofactors requires two lipoyl synthase-mediated sulfur insertions. We report the crystal structures of a lipoyl synthase complexed with S-adenosylhomocysteine or 5′-methylthioadenosine. Models based on these structures identify likely substrate-binding sites.

Substrate-binding sites in acetylcholinesterase

1991 ◽  
Vol 12 ◽  
pp. 422-426 ◽  
Author(s):  
Ferdinand Hucko ◽  
Jaak Järv ◽  
Christoph Weise
Keyword(s):  
Binding Sites ◽  
Substrate Binding ◽  
Substrate Binding Sites

scholarly journals Human organic anion transporter MRP4 (ABCC4) is an efflux pump for the purine end metabolite urate with multiple allosteric substrate binding sites

2005 ◽  
Vol 288 (2) ◽  
pp. F327-F333 ◽  
Author(s):  
Rémon A. M. H. Van Aubel ◽  
Pascal H. E. Smeets ◽  
Jeroen J. M. W. van den Heuvel ◽  
Frans G. M. Russel
Keyword(s):  
Binding Sites ◽  
Efflux Pump ◽  
Substrate Binding ◽  
Organic Anion ◽  
Apical Cell ◽  
Cell Uptake ◽  
Hek293 Cells ◽  
Hill Coefficient ◽  
Anion Transporter ◽  
Substrate Binding Sites

The end product of human purine metabolism is urate, which is produced primarily in the liver and excreted by the kidney through a well-defined basolateral blood-to-cell uptake step. However, the apical cell-to-urine efflux mechanism is as yet unidentified. Here, we show that the renal apical organic anion efflux transporter human multidrug resistance protein 4 (MRP4), but not apical MRP2, mediates ATP-dependent urate transport via a positive cooperative mechanism ( Km of 1.5 ± 0.3 mM, Vmax of 47 ± 7 pmol·mg−1·min−1, and Hill coefficient of 1.7 ± 0.2). In HEK293 cells overexpressing MRP4, intracellular urate levels were lower than in control cells. Urate inhibited methotrexate transport (IC50 of 235 ± 8 μM) by MRP4, did not affect cAMP transport, whereas cGMP transport was stimulated. Urate shifted cGMP transport by MRP4 from positive cooperativity ( Km and Vmax value of 180 ± 20 μM and 58 ± 4 pmol·mg−1·min−1, respectively, Hill coefficient of 1.4 ± 0.1) to single binding site kinetics ( Km and Vmax value of 2.2 ± 0.9 mM and 280 ± 50 pmol·mg−1·min−1, respectively). Finally, MRP4 could transport urate simultaneously with cAMP or cGMP. We conclude that human MRP4 is a unidirectional efflux pump for urate with multiple allosteric substrate binding sites. We propose MRP4 as a candidate transporter for urinary urate excretion and suggest that MRP4 may also mediate hepatic export of urate into the circulation, because of its basolateral expression in the liver.

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