2ptr
Crystal structure of Escherichia coli adenylosuccinate lyase mutant H171A with bound adenylosuccinate substrate
|
OverviewOverview
Adenylosuccinate lyase (ADL) catalyzes the breakdown of 5-aminoimidazole-, (N-succinylocarboxamide) ribotide (SAICAR) to, 5-aminoimidazole-4-carboxamide ribotide (AICAR) and fumarate, and of, adenylosuccinate (ADS) to adenosine monophosphate (AMP) and fumarate in, the de novo purine biosynthetic pathway. ADL belongs to the, argininosuccinate lyase (ASL)/fumarase C superfamily of enzymes. Members, of this family share several common features including: a mainly, alpha-helical, homotetrameric structure; three regions of highly conserved, amino acid residues; and a general acid-base catalytic mechanism with the, overall beta-elimination of fumarate as a product. The crystal structures, of wild-type Escherichia coli ADL (ec-ADL), and mutant-substrate, (H171A-ADS) and -product (H171N-AMP*FUM) complexes have been determined to, 2.0, 1.85, and 2.0 A resolution, respectively. The H171A-ADS and, H171N-AMP*FUM structures provide the first detailed picture of the ADL, active site, and have enabled the precise identification of substrate, binding and putative catalytic residues. Contrary to previous suggestions, the ec-ADL structures implicate S295 and H171 in base and acid catalysis, respectively. Furthermore, structural alignments of ec-ADL with other, superfamily members suggest for the first time a large conformational, movement of the flexible C3 loop (residues 287-303) in ec-ADL upon, substrate binding and catalysis, resulting in its closure over the active, site. This loop movement has been observed in other superfamily enzymes, and has been proposed to be essential for catalysis. The ADL catalytic, mechanism is re-examined in light of the results presented here.
About this StructureAbout this Structure
2PTR is a Single protein structure of sequence from Escherichia coli with as ligand. Active as Adenylosuccinate lyase, with EC number 4.3.2.2 Full crystallographic information is available from OCA.
ReferenceReference
Substrate and Product Complexes of Escherichia coli Adenylosuccinate Lyase Provide New Insights into the Enzymatic Mechanism., Tsai M, Koo J, Yip P, Colman RF, Segall ML, Howell PL, J Mol Biol. 2007 Jul 13;370(3):541-554. Epub 2007 May 4. PMID:17531264
Page seeded by OCA on Wed Jan 23 14:41:04 2008