1dje: Difference between revisions

{{STRUCTURE_1dje|  PDB=1dje  |  SCENE= }}

 

'''CRYSTAL STRUCTURE OF THE PLP-BOUND FORM OF 8-AMINO-7-OXONANOATE SYNTHASE'''

 

 

==Overview==

8-Amino-7-oxononanoate synthase (also known as 7-keto-8-aminopelargonate synthase, EC 2.3.1.47) is a pyridoxal 5'-phosphate-dependent enzyme which catalyzes the decarboxylative condensation of L-alanine with pimeloyl-CoA in a stereospecific manner to form 8(S)-amino-7-oxononanoate. This is the first committed step in biotin biosynthesis. The mechanism of Escherichia coli AONS has been investigated by spectroscopic, kinetic, and crystallographic techniques. The X-ray structure of the holoenzyme has been refined at a resolution of 1.7 A (R = 18.6%, R(free) = 21. 2%) and shows that the plane of the imine bond of the internal aldimine deviates from the pyridine plane. The structure of the enzyme-product external aldimine complex has been refined at a resolution of 2.0 A (R = 21.2%, R(free) = 27.8%) and shows a rotation of the pyridine ring with respect to that in the internal aldimine, together with a significant conformational change of the C-terminal domain and subtle rearrangement of the active site hydrogen bonding. The first step in the reaction, L-alanine external aldimine formation, is rapid (k(1) = 2 x 10(4) M(-)(1) s(-)(1)). Formation of an external aldimine with D-alanine, which is not a substrate, is significantly slower (k(1) = 125 M(-)(1) s(-)(1)). Binding of D-alanine to AONS is enhanced approximately 2-fold in the presence of pimeloyl-CoA. Significant substrate quinonoid formation only occurs upon addition of pimeloyl-CoA to the preformed L-alanine external aldimine complex and is preceded by a distinct lag phase ( approximately 30 ms) which suggests that binding of the pimeloyl-CoA causes a conformational transition of the enzyme external aldimine complex. This transition, which is inferred by modeling to require a rotation around the Calpha-N bond of the external aldimine complex, promotes abstraction of the Calpha proton by Lys236. These results have been combined to form a detailed mechanistic pathway for AONS catalysis which may be applied to the other members of the alpha-oxoamine synthase subfamily.

 

==About this Structure==

1DJE is a [[Single protein]] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1DJE OCA].  

 

==Reference==

Mechanism of 8-amino-7-oxononanoate synthase: spectroscopic, kinetic, and crystallographic studies., Webster SP, Alexeev D, Campopiano DJ, Watt RM, Alexeeva M, Sawyer L, Baxter RL, Biochemistry. 2000 Jan 25;39(3):516-28. PMID:[http://www.ncbi.nlm.nih.gov/pubmed/10642176 10642176]

[[Category: Single protein]]

[[Category: Alexeev, D.]]

[[Category: Alexeeva, M.]]

[[Category: Baxter, R L.]]

[[Category: Campopiano, D J.]]

[[Category: Sawyer, L.]]

[[Category: Watt, R M.]]

[[Category: Webster, S P.]]

[[Category: 8-amino-7-ketopelargonate synthase]]